A method and apparatus for VVT minimum target phase control

Abstract

The application discloses a VVT minimum target phase control method, and steps are as follows: determining a basic VVT minimum phase: by controlling VVT activation and reducing a VVT target phase, comparing a phase initial value and fuel consumption difference when the VVT phase is 0, and determining the basic VVT minimum phase; determining an original VVT minimum phase: correcting the basic VVT minimum phase to obtain the original VVT minimum phase; VVT minimum phase self-learning: sequentially entering a self-learning stabilization stage, a self-learning activation stage, a self-learning updating stage and a self-learning storage stage, storing VVT minimum phase learning coefficients in an EEPROM in each working condition and correcting the VVT minimum phase learning coefficients to obtain a final VVT minimum phase. The application also discloses a VVT minimum target phase control device. The application can be widely applied to the engine control field and avoids power and emission problems caused by too small target setting in the VVT target setting process.

Description

Technical Field

[0001] This invention relates to the field of engine control, and in particular to a method and apparatus for VVT minimum target phase control. Background Technology

[0002] Studies have shown that VVT systems offer significant advantages in terms of power under full load conditions and fuel economy under partial load conditions. However, after VVT control is activated, if the VVT ​​phase is too small, the current to the VVT ​​control solenoid valve will also decrease, easily causing fluctuations in the actual VVT phase. Furthermore, if the VVT ​​phase is close to the lock-up position, oil pressure fluctuations are also likely, potentially leading to similar fluctuations in the actual VVT phase.

[0003] In view of this, an invention with application number "CN202011247319.6" and invention title "A Calculation Method and System for Target VVT Phase" determines the basic target VVT phase based on engine speed and load; obtains the corresponding correction rate based on special operating conditions; determines the initial target VVT phase based on the basic target VVT phase and each correction rate; determines whether VVT is activated based on VVT activation state conditions; classifies VVT states based on the judgment results, and determines the final target VVT phase. This invention calculates the initial target VVT phase from throttle opening, manifold pressure difference, and minimum ignition angle, which can accurately calculate the target VVT phase, and introduces VVT control activation conditions to perform a secondary correction on the final target VVT phase. Although this invention adjusts the change of VVT phase according to the ignition angle, it does not consider the design method of the minimum VVT phase.

[0004] Another invention, with application number "CN202110717601.4" and titled "Calculation Method, Computer Equipment and Storage Medium for Basic Ignition Efficiency of Engine," updates the basic ignition efficiency of the engine based on gas volume learning. However, similarly, this solution also does not consider the design method for the minimum phase of VVT.

[0005] Therefore, it is necessary to introduce the control of the minimum target phase of VVT, which is the minimum target phase when VVT is activated, to avoid fluctuations in the actual phase of VVT and the resulting fluctuations in gas volume, which would lead to unstable dynamics and deterioration of emission control. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a VVT minimum target phase control method and device, which shuts down the VVT ​​control system when the VVT ​​target phase is lower than the final VVT minimum phase, that is, does not allow VVT to be activated, thus avoiding power and emission problems caused by the target setting being too small during the VVT ​​target setting process.

[0007] The present invention provides a VVT minimum target phase control method, comprising the following steps: determining the basic VVT minimum phase. Minimum phase of basic VVT The calibration results were obtained from engine bench calibration. The calibration was based on the following: when the catalytic converter ignition was complete and the coolant temperature was at warm-up temperature, the VVT ​​was activated and the target VVT phase was reduced. The difference in fuel consumption between the initial value of the minimum VVT phase and the value when the VVT ​​phase was 0 was compared to determine the basic minimum VVT phase. Determine the minimum phase of the original VVT. : Minimum phase of the basic VVT Corrections are made under various vehicle operating conditions to obtain the original VVT minimum phase of the entire vehicle. VVT minimum phase self-learning: When the engine operating conditions are stable, VVT minimum phase self-learning is performed. Under the premise of meeting the VVT ​​minimum phase self-learning activation conditions, it sequentially enters the VVT ​​minimum phase self-learning stabilization stage, VVT minimum phase self-learning activation stage, VVT minimum phase self-learning update stage, and VVT minimum phase self-learning storage stage, storing the VVT ​​minimum phase learning coefficients for each operating condition. All values ​​are stored in the EEPROM and corrected to obtain the final minimum phase of VVT. .

[0008] In the above technical solution, the activation conditions for the VVT ​​minimum phase self-learning step are as follows: Engine running time: The engine is running, and the engine running time exceeds a first preset time; Closed-loop control: The VVT ​​system is in a closed-loop control activated state; Preset phase difference: The current VVT target phase. The difference between the target and VVT minimum phases does not exceed a preset range; Carbon canister: The carbon canister is not open; Cylinder intake air density: The target fresh air intake density entering the cylinder is within a certain range, and the fluctuation of the target fresh air intake density entering the cylinder after self-learning the VVT ​​minimum phase is small; Engine coolant temperature fluctuation: The engine coolant temperature is within a certain range, and the fluctuation of the engine coolant temperature after self-learning the VVT ​​minimum phase is small; Intake air temperature fluctuation: The intake air temperature is within a certain range, and the fluctuation of the intake air temperature after self-learning the VVT ​​minimum phase is small; Oil temperature fluctuation: The oil temperature is within a certain range, and the fluctuation of the oil temperature after self-learning the VVT ​​minimum phase is small. The self-learning process for minimum phase results in minimal oil temperature fluctuation; oil pressure fluctuation: oil pressure is within a certain range, and the oil pressure fluctuation is minimal when entering the VVT ​​minimum phase self-learning process; engine speed closed-loop control: engine speed enters closed-loop control; engine target speed fluctuation: engine target speed is within a certain range, and the engine target speed fluctuation is minimal when entering the VVT ​​minimum phase self-learning process; crankshaft forced ventilation on / off status: crankshaft forced ventilation function on / off status remains unchanged; knocking or pre-ignition: no knocking or pre-ignition occurs; intake air density fluctuation: the intake air density fluctuation of the target fresh air entering the cylinder is minimal.

[0009] In the above technical solution, the specific process of the VVT ​​minimum phase self-learning stabilization stage in the VVT ​​minimum phase self-learning step is as follows: Second preset time T0 judgment: Determine whether entering the VVT ​​minimum phase self-learning stabilization stage exceeds the second preset time T0; Third preset time T1 judgment: Determine whether the VVT ​​minimum phase self-learning non-update time interval exceeds the third preset time T1; Maintain current stage: If the conditions of the second preset time T0 judgment and the third preset time T1 judgment are not met, but the activation condition is met, then maintain in the VVT ​​minimum phase self-learning stabilization stage; Return to previous stage: If the conditions of the second preset time T0 judgment and the third preset time T1 judgment are not met, and the activation condition is not met, then re-determine whether the VVT ​​minimum phase self-learning activation condition is met; Enter next stage: If the conditions of the second preset time T0 judgment and the third preset time T1 judgment are met, and the activation condition is met, then enter the VVT ​​minimum phase self-learning activation stage.

[0010] In the above technical solution, the specific process of the VVT ​​minimum phase self-learning activation phase in the VVT ​​minimum phase self-learning step is as follows: When entering the VVT ​​minimum phase self-learning activation phase, the total engine speed, total intake air temperature, total coolant temperature, total oil temperature, total oil pressure, total target intake air density, total actual intake air density, and total target engine speed are calculated cumulatively within the cumulative time T2. Total and actual engine speed filtering Total value, target engine fire circuit torque Total, actual engine firing torque Once the sum of the VVT ​​target phase and the sum of the VVT ​​actual phase are satisfied within the cumulative time T2, the VVT ​​minimum phase self-learning update phase begins.

[0011] In the above technical solution, during the VVT ​​minimum phase self-learning activation phase of the VVT ​​minimum phase self-learning step, the actual engine speed is filtered. The value is calculated as follows: ,in, This is the original value of the actual engine speed. This represents the original value of the actual engine speed during the Nth sampling period. This is the actual engine speed filtered value after first-order low-pass filtering. This is the filtered value of the actual engine speed in the Nth sampling period. This represents the filtered value of the actual engine speed in the (N-1)th sampling period, where N = 1, 2, 3… The original value of the actual engine speed at the moment of entering the self-learning activation phase. , This refers to the engine speed filtering coefficient.

[0012] In the above technical solution, the specific process of the VVT ​​minimum phase self-learning update stage in the VVT ​​minimum phase self-learning step is as follows: When the intake air temperature, water temperature, oil temperature, oil pressure, engine target speed, target fresh air intake density, and VVT target phase are the same as the set values ​​of the aforementioned parameters, it is set as the same operating condition; the VVT ​​minimum phase learning coefficient under each operating condition is... All are stored in EEPROM.

[0013] In the above technical solution, the specific process of the VVT ​​minimum phase self-learning storage stage in the VVT ​​minimum phase self-learning step is as follows: Average value calculation: Calculate the average intake air temperature, average coolant temperature, average oil temperature, average oil pressure, and average engine target speed during the cumulative time T2 segment within the VVT ​​minimum phase self-learning stage. Average value of actual engine speed filter The average density of fresh air entering the cylinder. Average density of fresh air entering the cylinder Target engine fire circuit average torque Actual engine firing average torque VVT target phase average value , VVT actual phase average Operating condition update: Update the average intake air temperature to the corresponding intake air temperature operating condition, update the average coolant temperature to the corresponding coolant temperature operating condition, update the average oil temperature to the corresponding oil temperature operating condition, update the average oil pressure to the corresponding oil pressure operating condition, update the average engine target speed to the corresponding engine target speed operating condition, update the learned value of the target intake air density into the cylinder to the corresponding target intake air density into the cylinder operating condition, update the learned value of the VVT ​​target phase operating condition to the corresponding VVT target phase operating condition, and store each updated value in the EEPROM.

[0014] In the above technical solution, the specific process of the working condition update step in the VVT ​​minimum phase self-learning step, specifically the VVT ​​minimum phase self-learning storage stage, is as follows: VVT minimum phase learning value Correction method: , , , The classification is as follows: Based on the aforementioned formula, C1 is determined to be the minimum target phase correction coefficient for VVT based on gas volume. C1 is divided into four levels, see Table 1: Table 1

[0015]

[0016] Based on the aforementioned formula, C2 is determined to be the minimum target phase correction coefficient for VVT based on rotational speed. C2 is divided into four levels, see Table 2: Table 2

[0017]

[0018] Based on the aforementioned formula, C3 is determined to be the minimum target phase correction coefficient for torque-based VVT. C3 is divided into six levels, see Table 3: Table 3

[0019]

[0020] Based on the aforementioned formula, C4 is determined to be the minimum target phase correction coefficient for VVT based on VVT control accuracy. C4 is divided into seven levels, see Table 4: Table 4

[0021]

[0022] Calculate the minimum phase learning coefficients for VVT When C1, C2, C3, and C4 meet the corresponding levels, the corresponding number of self-learning updates, Cnt, is... NAdd 1, only once during each learning process, and perform VVT minimum phase learning at most once per driving cycle, then the final VVT minimum phase learning coefficient is... : ,in, The minimum phase learning coefficient of VVT learned under the same operating conditions in the previous operation; ,in, Initial values ​​of VVT minimum phase learning coefficients This represents the maximum number of updates. The minimum target phase correction coefficient for VVT is defined based on various features, where N = 1, 2, 3, 4, and the features include load, engine speed, torque, and VVT accuracy. , , , ,in, The minimum target phase correction coefficient for VVT is defined based on various features, where N = 1, 2, 3, 4, and the features include load, engine speed, torque, and VVT accuracy; if Cnt N Less than At that time, = ; The data will be stored in the EEPROM after the vehicle is powered off. Updated under the same working conditions last time The initial default value is 0; once Cnt... N = ,but = And Cnt N Reset to 0, where f is the update iteration coefficient; the final learned VVT minimum phase learning coefficient after constraint. The corresponding operating condition is stored in the EEPROM, and the final minimum phase of VVT is calculated. Then the minimum phase of the final VVT is obtained. When the target phase of VVT is lower than the minimum phase of the final VVT At this time, the VVT ​​control system is turned off, that is, VVT activation is not allowed, and the final VVT minimum phase is turned off. This serves as the minimum limit when setting the target phase for VVT.

[0023] In the above technical solution, the determination of the original VVT minimum phase The specific steps are as follows: First multiplication factor: Determine the first multiplication factor based on real-time atmospheric pressure and real-time oil temperature. Second multiplication factor: Determined based on engine combustion cycles and atmospheric temperature. Third multiplication factor: Determined based on real-time coolant temperature and engine starting coolant temperature. Fourth multiplication factor: Determine the fourth multiplication factor based on real-time water temperature and intake air temperature. Fifth multiplication factor: Determined based on the mass flow rate of fuel vapor entering the cylinder from the carbon canister and the engine speed. The sixth multiplication factor is determined based on the oil pressure and the rate of change of oil pressure. The seventh multiplication factor: Determine the seventh multiplication factor based on the crankshaft forced ventilation function's on / off status. Eighth multiplication factor: based on engine speed and load fluctuation coefficient. Determine the eighth multiplication factor Among them, load fluctuation coefficient The method for determining it is as follows: ,in, This refers to the actual fresh air intake density entering the cylinder. This represents the actual fresh air intake density entering the cylinder during the Nth sampling period. This represents the actual fresh air intake density entering the cylinder after a first-order low-pass filter. This represents the filtered actual fresh air intake density entering the cylinder during the Nth sampling period. The filtered actual fresh air intake density entering the cylinder during the (N-1)th sampling period, where N = 1, 2, 3… This equals the actual fresh air intake density entering the cylinders immediately after the engine has successfully started. , Load fluctuation filter coefficients: ,in The number of engine cylinders. Engine speed, Gas volume filtering coefficient; load fluctuation coefficient The original VVT minimum phase of the whole vehicle :

[0024] .

[0025] The present invention also provides a VVT minimum target phase control device having a computer program that can execute a VVT minimum target phase control method.

[0026] The VVT ​​minimum target phase control method and apparatus of the present invention have the following beneficial effects:

[0027] Without affecting the normal operation of the engine, regardless of differences in engine manufacturing or engine life cycle, the minimum phase of VVT can be self-learned without actively adjusting parameters. This is designed from the perspective of improving fuel economy, and at the same time, the stability of the VVT ​​control system is improved without affecting emissions. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall process of the VVT ​​minimum target phase control method of the present invention;

[0029] Figure 2 This is a flowchart illustrating the step of determining the minimum phase of the basic VVT in the VVT ​​minimum target phase control method of the present invention.

[0030] Figure 3 This is a flowchart illustrating the step of determining the original minimum VVT phase in the VVT ​​minimum target phase control method of the present invention.

[0031] Figure 4 This is a flowchart illustrating the VVT ​​minimum phase self-learning step in the VVT ​​minimum target phase control method of the present invention.

[0032] Figure 5 This is a schematic diagram of the structure of the VVT ​​minimum target phase control device of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention.

[0034] The purpose of this invention is to solve the power and emission problems caused by setting the VVT ​​target phase too low when the VVT ​​target phase is lower than the VVT ​​minimum phase by shutting down the VVT ​​control system, i.e., disallowing VVT activation, as the minimum limit when setting the VVT ​​target phase.

[0035] Generally, a camshaft phasing control system mainly consists of a camshaft phaser, a camshaft position sensor, a coolant temperature sensor, a camshaft timing hydraulic control valve (OCV), a crankshaft position sensor, and an electronic control unit (ECU). The camshaft phaser primarily consists of rotor blades, a stator, and a return spring. The rotor blades are fixed to the intake camshaft, and the stator is integrated with the driven timing sprocket. When the oil in the system's oil circuit is pressurized by the timing hydraulic control valve, the oil compresses the rotor and drives the intake camshaft to rotate, causing the camshaft phase to advance, lag, or remain in place, thereby changing the opening and closing times of the intake valves. During the rotor's movement, the phaser forms two hydraulic chambers: a valve timing advance chamber and a valve timing lag chamber. Additionally, an oil pressure sensor and / or a variable displacement oil pump can be added to this system. The oil pressure sensor reads the oil pressure in the main oil passage, while the variable displacement oil pump adjusts the oil pressure.

[0036] See Figure 1 The present invention provides a VVT minimum target phase control method, comprising the following steps:

[0037] See Figure 2 1. Determine the minimum phase of the basic VVT Minimum phase of basic VVT The values ​​were obtained from engine bench calibration. The calibration criteria were as follows: when the catalytic converter ignition was complete and the coolant temperature was at warm-up temperature, the VVT ​​was first activated by strong control (after activation, the actual VVT phase will follow the target VVT phase; when deactivated, the actual VVT phase will not follow the target VVT phase) and the target VVT phase was reduced (until, under steady-state conditions, the engine speed fluctuation was no less than ±30 rpm, or misfire occurred in any cylinder, or the difference between the target VVT phase and the actual VVT phase exceeded ±1°, at which point the VVT ​​phase reduction was stopped, and the minimum VVT phase was taken as the initial value of the minimum VVT phase. Here, steady-state conditions refer to engine target speed fluctuations not exceeding ±5 rpm and engine requested firing torque fluctuations not exceeding ±2 Nm).

[0038] Secondly, the difference in fuel consumption was compared between the initial value of the VVT ​​minimum phase and when the VVT ​​phase was 0. If the fuel consumption improvement exceeded 0.02% at the VVT ​​phase corresponding to the initial value of the VVT ​​minimum phase, then the base VVT ​​minimum phase... It equals the initial value of the minimum phase of VVT; if the improvement in fuel consumption does not exceed 0.02% under the VVT ​​phase corresponding to the initial value of the minimum phase of VVT, then the basic minimum phase of VVT is... It equals 0.

[0039] In this embodiment, the following results were obtained based on the engine speed and load (actual fresh air intake density) obtained using the above experimental method. Taking intake VVT ​​as an example, the exhaust VVT control method is the same, as detailed in Table 1 below:

[0040] Table 1

[0041]

[0042] See Figure 3 2. Determine the minimum phase of the original VVT The basic VVT minimum phase is corrected under different vehicle operating conditions to obtain the original VVT minimum phase of the vehicle. :

[0043] 1. Determine the first multiplication factor based on real-time atmospheric pressure and real-time oil temperature. The lower the atmospheric pressure or the lower the water temperature, the thinner the air, resulting in poorer engine combustion stability. Alternatively, low oil temperature can cause the VVT ​​phaser to become viscous, making it less sensitive. Therefore, it is necessary to increase the minimum phase of VVT to reduce the impact on engine combustion stability and VVT phase control accuracy, and avoid abnormal engine vibration.

[0044] 2. Determine the second multiplication factor based on the engine combustion count (the sum of the number of ignitions in each cylinder from engine start-up) and atmospheric temperature. The fewer the number of combustion cycles or the lower the atmospheric temperature, the worse the engine combustion stability. It is necessary to increase the minimum phase of VVT to reduce the impact on engine combustion stability and avoid abnormal engine vibration.

[0045] 3. Determine the third multiplication factor based on the real-time coolant temperature and the engine start-up coolant temperature (coolant temperature at the moment the engine is started). The lower the real-time coolant temperature or the lower the engine starting coolant temperature, the worse the engine combustion stability. It is necessary to increase the minimum phase of VVT to reduce the impact on engine combustion stability and avoid abnormal engine vibration.

[0046] 4. Determine the fourth multiplication factor based on real-time water temperature and intake air temperature. The lower the real-time coolant temperature or the lower the engine intake air temperature, the worse the engine combustion stability. It is necessary to increase the minimum phase of VVT to reduce the impact on engine combustion stability and avoid abnormal engine vibration.

[0047] 5. Determine the fifth multiplication factor based on the mass flow rate of fuel vapor entering the cylinder from the carbon canister and the engine speed. The lower the engine speed, the more fuel vapor mass flow rate enters the cylinder from the carbon canister, resulting in poorer engine combustion stability. Therefore, it's necessary to increase the minimum VVT phase to reduce the impact on engine combustion stability and avoid abnormal engine vibration.

[0048] 6. Determine the sixth multiplication factor based on the oil pressure and the rate of change of oil pressure. The lower the oil pressure and the smaller the rate of change of oil pressure, the worse the control accuracy of the VVT ​​phaser. It is necessary to increase the minimum phase of the VVT ​​to reduce the impact on the engine combustion stability and avoid abnormal engine vibration.

[0049] 7. Determine the seventh multiplication factor based on the crankshaft forced ventilation function's on / off status. When the crankshaft forced ventilation function is on, fluctuations in the intake pressure of the intake system can affect the accuracy of VVT phase control. Therefore, the minimum phase of VVT is increased to prevent abnormal engine vibration. When the crankshaft forced ventilation function is off, the seventh multiplication factor... =0.

[0050] 8. Based on the fluctuation coefficient of engine speed and load (actual intake air density into the cylinder) Determine the eighth multiplication factor The higher the engine speed and the greater the load fluctuation coefficient, the greater the transient changes in the operating conditions. To avoid a significant impact on the airflow impact on the valves, it is necessary to increase the minimum phase of the VVT.

[0051] Among them, load fluctuation coefficient The method for determining it is as follows:

[0052]

[0053] in, This refers to the actual fresh air intake density entering the cylinder. This represents the actual fresh air intake density entering the cylinder during the Nth sampling period. This represents the actual fresh air intake density entering the cylinder after a first-order low-pass filter. This represents the filtered actual fresh air intake density entering the cylinder during the Nth sampling period. The filtered actual fresh air intake density entering the cylinder during the (N-1)th sampling period, where N = 1, 2, 3… Equal to the actual fresh air intake density entering the cylinder during the 0th sampling period Furthermore, the 0th sampling period occurs immediately after the engine has successfully started; in this example, this means the engine speed is greater than 750 rpm for the first time in this driving cycle. Sampling period interval... In this example, it took 10ms. Load fluctuation filter coefficients: (The engine in this example has 4 cylinders.) The calibration speed is 1000 rpm. The purpose of this setting is for normalization; no special calibration is needed for different numbers of cylinders and engine speeds. Only the 4-cylinder engine and the engine at 1000 rpm need to be calibrated. (thus reducing calibration testing work), among which The number of engine cylinders. Engine speed, This is the gas flow filtering coefficient; in this example, it is set to 0.02.

[0054] From the above, we can see that the load fluctuation coefficient .

[0055] The first, second, third, fourth, fifth, sixth, seventh, and eighth multiplication factors mentioned above aim to improve combustion stability and VVT phase control accuracy during the VVT ​​control process based on the engine's current operating conditions. When engine operating conditions are adverse (e.g., insufficient temperature and pressure signals, poor engine combustion, carbon canister flow interference, intake air fluctuation interference, oil pressure interference, crankshaft ventilation interference, etc.), it is necessary to increase the minimum VVT phase to improve combustion stability and VVT phase control accuracy. When engine combustion is better after temperature increases, the aim is to reduce the minimum VVT phase to improve VVT ​​fuel economy. Based on the above concepts, existing technical solutions are used to determine the first to eighth multiplication factors.

[0056] The determination methods for all eight multiplication factors (all of which are values ​​greater than or equal to 0) are all based on ensuring that the engine combustion stability evaluation index COV is within ±3% and the VVT ​​phase control accuracy (the absolute value of the difference between the target VVT phase and the actual VVT phase divided by the target phase does not exceed ±1%).

[0057] Ultimately, the original VVT minimum phase of the entire vehicle Pick:

[0058] .

[0059] See Figure 4 Third, VVT minimum phase self-learning: As the engine's lifespan progresses, components age and control parameters may deviate in performance. VVT minimum phase self-learning is performed when the engine's operating conditions are stable to ensure accuracy. The self-learning process can begin once the most basic prerequisites are met.

[0060] The minimum phase self-learning activation condition for VVT is as follows:

[0061] 1. The engine is running, and the engine running time exceeds the first preset time, which is 5 minutes in this example;

[0062] 2. The VVT ​​system is in closed-loop control active state (at this time, the actual phase of VVT is controlled to follow the target phase of VVT).

[0063] 3. Current VVT target phase The minimum phase of VVT (or the original minimum phase of VVT for the entire vehicle if not learned). If it has been learned, then the difference between the learned and updated minimum phase of VVT and the minimum phase should not exceed the preset range; in this example, it is ±0.5°.

[0064] 4. The carbon canister is not open;

[0065] 5. The target fresh air intake density entering the cylinder is within a certain range, which in this example is between 200 mgpl and 3000 mgpl. The target fresh air intake density entering the cylinder fluctuates little when entering the minimum phase of VVT. In this example, it is ±10 mgpl.

[0066] 6. The engine coolant temperature is within a certain range (0℃ to 100℃ in this example), and the engine coolant temperature fluctuation is small when entering the VVT ​​minimum phase self-learning stage; in this example, ±2℃ is used.

[0067] 7. The intake air temperature is within a certain range (30℃ to 80℃ in this example), and the intake air temperature fluctuation during self-learning to enter the minimum phase of VVT is small; in this example, it is ±1.5℃.

[0068] 8. The oil temperature is within a certain range (30℃ to 80℃ in this example), and the oil temperature fluctuation during the self-learning of the minimum phase of VVT is small. In this example, it is ±1.5℃.

[0069] 9. The oil pressure is within a certain range (100 kPa to 380 kPa in this example), and the oil pressure fluctuation during self-learning when entering the minimum phase of VVT is small (±5 kPa in this example).

[0070] 10. Engine speed enters closed-loop control;

[0071] 11. The target engine speed is within a certain range, which is between 600 rpm and 5900 rpm in this example. The target engine speed fluctuation is small when entering the VVT ​​minimum phase self-learning, which is ±5 rpm in this example.

[0072] 12. The crankshaft forced ventilation function remains in the same state (i.e., it is either on or off).

[0073] 13. No detonation or pre-ignition occurred;

[0074] 14. The density fluctuation of the fresh air entering the cylinder is small; in this example, it is taken as ±10 mgpl.

[0075] If any activation condition is not met at any stage of the self-learning process, the self-learning process terminates and enters the inactive self-learning stage. When the activation conditions are met, the self-learning process based on the minimum phase of VVT can be attempted, first entering the self-learning stabilization stage of the minimum phase of VVT.

[0076] VVT minimum phase self-learning stabilization stage:

[0077] When entering the VVT ​​minimum phase self-learning stabilization phase, the purpose of the stabilization phase is to ensure that the self-learning activation conditions are stable and reliable. The VVT ​​minimum phase self-learning activation phase will begin when the following conditions are met during the VVT ​​minimum phase self-learning stabilization phase.

[0078] 1. The self-learning stabilization phase takes longer than the second preset time T0, which is 5 seconds in this example;

[0079] 2. The self-learning of the minimum phase of VVT has not been updated for more than the third preset time T1 (in this embodiment, it is 7200h; the self-learning count is updated once the self-learning of the minimum phase of VVT is completed. If the learning interval is too long, the difference in the learning value each time may be caused by the aging of engine parts, rather than the learning of accurate information).

[0080] If the above two conditions are not met, but the activation condition is met, the system remains in the VVT ​​minimum phase self-learning stabilization stage; if the above two conditions are not met, and the activation condition is not met, the system returns to the self-learning inactive stage; if the above two conditions are met, and the activation condition is met, the system enters the next stage, namely the VVT ​​minimum phase self-learning activation stage.

[0081] VVT minimum phase self-learning activation phase:

[0082] During the self-learning activation phase of VVT minimum phase, the following parameters are cumulatively calculated within the cumulative time T2 (3s in this embodiment): total engine speed, total intake air temperature, total coolant temperature, total oil temperature, total oil pressure, total target intake air density, total actual intake air density, and total target engine speed. Total and actual engine speed filtering Sum of values ​​(algorithm as follows), target engine fire circuit torque Total, actual engine firing torque The sum of the VVT ​​target phase and the sum of the VVT ​​actual phase. After the cumulative time T2 is satisfied, the next stage begins, namely the VVT ​​minimum phase self-learning update stage.

[0083] In this embodiment, the actual engine speed filter value The calculation method is as follows:

[0084]

[0085] in, This is the original value of the actual engine speed. This represents the original value of the actual engine speed during the Nth sampling period. This is the actual engine speed after first-order low-pass filtering (i.e., the actual filtered engine speed value). This is the filtered value of the actual engine speed in the Nth sampling period. This represents the filtered value of the actual engine speed in the (N-1)th sampling period, where N = 1, 2, 3… This is equal to the original value of the actual engine speed at the 0th sampling period (the 0th sampling period refers to the moment when the self-learning activation phase has just begun). Sampling period interval In this example, it took 10ms. This is the engine speed filtering coefficient; in this example, it is set to 0.1.

[0086] VVT minimum phase self-learning update phase:

[0087] When intake air temperature, coolant temperature, engine oil temperature, oil pressure, engine target speed, target fresh air intake density, and VVT target phase are all the same, they are considered to be operating under the same condition. "Same" is defined as a deviation not exceeding ±1%. For example, if the difference between two engine target speeds divided by the smallest engine target speed does not exceed ±1%, then the two engine target speeds are considered to be the same. The VVT ​​minimum phase learning coefficient is used for each operating condition. All values ​​will be stored in the non-volatile memory EEPROM (the EEPROM will have an initial default value of 1, which means that the stored value in the EEPROM will be automatically updated after the VVT ​​minimum phase self-learning is completed).

[0088] The VVT ​​minimum phase self-learning storage stage mainly completes the following tasks:

[0089] 1. Average value calculation: Calculate the average intake air temperature, average coolant temperature, average engine oil temperature, average engine oil pressure, and average engine target speed during the cumulative time T2 segment of the VVT ​​minimum phase self-learning phase. Average value of actual engine speed filter The average density of fresh air entering the cylinder. Average density of fresh air entering the cylinder Target engine fire circuit average torque Actual engine firing average torque VVT target phase average value , Actual phase average of VVT .

[0090] 2. Operating Condition Update: The average intake air temperature, average coolant temperature, average oil temperature, average oil pressure, average engine target speed, target intake air density, and VVT target phase are updated to the EEPROM of the corresponding operating conditions (intake air temperature, coolant temperature, oil temperature, oil pressure, engine target speed, target intake air density, and VVT target phase).

[0091] In this embodiment, the specific update method for the operating condition update step is as follows:

[0092] 1. Minimum phase learning value of VVT Correction method:

[0093]

[0094]

[0095] The method for determining C3 does not take an absolute value. In practice, the larger the torque in the fire circuit, the better the fuel economy. In order to determine the torque-based correction method later, this design does not take an absolute value.

[0096]

[0097] It should be noted that in this example, the design standard for C1 is 2%, meaning that C1 is considered normal and reasonable when it does not exceed 2%. Similarly, the design standard for C2 is 1.5%; the design standard for C3 is 5%; and the design standard for C4 is 1%.

[0098] If C1 is too large, it indicates that the gas volume control fluctuates greatly, and the minimum phase of VVT needs to be increased. At this time, the phase is too small and the control is unstable. If C1 is too small, that is, the deviation is less than the design standard, it indicates that the gas volume control fluctuates very little, and the minimum phase of VVT can be reduced to increase the operating range of VVT and make full use of the fuel economy advantage of VVT.

[0099] If C2 is too large, it indicates that the speed control fluctuates greatly, and the minimum phase of VVT needs to be increased. At this time, the phase is too small and the control is unstable. If C2 is too small, that is, the deviation is less than the design standard, it indicates that the speed control fluctuates very little, and the minimum phase of VVT can be reduced to increase the operating range of VVT and make full use of the fuel economy advantage of VVT.

[0100] If C3 is too large and not positive, it indicates significant torque control fluctuations, requiring an increase in the VVT ​​minimum phase. However, a too-small phase in this case leads to unstable control. Conversely, if C3 is too small and positive (i.e., the deviation is less than the design standard), it indicates minimal torque control fluctuations, allowing for a reduction in the VVT ​​minimum phase, thus expanding the VVT's operating range and fully utilizing its fuel economy advantages. Finally, if C3 is negative, it indicates that the VVT ​​has improved fuel economy and increased the engine's actual torque, allowing for a further reduction in the VVT ​​minimum phase, further expanding its operating range and fully leveraging its fuel economy advantages.

[0101] If C4 is too large, it indicates that the VVT ​​phase control fluctuates greatly, and the minimum phase of VVT needs to be increased. At this time, the phase is too small and the control is unstable. If C4 is too small, that is, the deviation is less than the design standard, it indicates that the VVT ​​phase control fluctuates very little, and the minimum phase of VVT can be reduced to increase the operating range of VVT and make full use of the fuel economy advantage of VVT.

[0102] Level Classification: Based on the aforementioned formula, C1 is divided into four levels. Level 1 is when the absolute value of C1 differs from its design standard by more than 1%, indicating extremely large gas volume fluctuations. Level 2 is when the absolute value of C1 differs from its design standard by no more than 1% but more than 0.2%, indicating moderate gas volume fluctuations. Level 3 is when the absolute value of C1 differs from its design standard by no more than 0.2% but more than 0%, indicating normal gas volume fluctuations. Level 4 is when the absolute value of C1 differs from its design standard by no more than 0%, indicating extremely small gas volume fluctuations.

[0103] C1 is determined as the minimum target phase correction coefficient for VVT based on gas volume. See Table 2 below for details:

[0104] Table 2

[0105]

[0106] Similarly, based on the aforementioned formula, C2 is determined to be the minimum target phase correction coefficient for VVT based on rotational speed. C2 is divided into four levels, as detailed in Table 3 below:

[0107] Table 3

[0108]

[0109] Similarly, based on the aforementioned formula, C3 is determined to be the minimum target phase correction coefficient for torque-based VVT. C3 has a significant impact on fuel economy. To optimize its impact on fuel economy, C3 is divided into 6 levels, as shown in Table 4 below:

[0110] Table 4

[0111]

[0112] Similarly, based on the aforementioned formula, C4 is determined to be the minimum target phase correction coefficient for VVT based on VVT control accuracy. Unstable VVT ​​control can negatively impact emissions and fuel consumption, significantly affecting fuel economy. To optimize the impact on emissions and fuel economy, C4 is divided into 7 levels, as detailed in Table 5 below:

[0113] Table 5

[0114]

[0115] When C1, C2, C3, and C4 meet the corresponding levels, the corresponding phase learning update count Cnt is... N Add 1 (where the index N corresponds to arrays 1, 2, 3, and 4 in C1, C2, C3, and C4 respectively), and Cnt is incremented during each learning process. N It is added only once, and VVT minimum phase learning is performed at most once in each driving cycle.

[0116] Calculate the minimum phase learning coefficients for VVT The specific process is as follows:

[0117] in This is the minimum phase learning value of VVT learned under the same operating conditions in the previous time, and its initial default value is 1.

[0118] ,

[0119] in, Initial values ​​of VVT minimum phase learning coefficients The maximum number of updates is set to 10,000 in this example. The minimum target phase correction coefficient for VVT is based on various features (N=1,2,3,4), where features include air volume (load), engine speed, torque, and VVT accuracy.

[0120] , , , ,in, The minimum target phase correction coefficient for VVT is based on various features (N=1,2,3,4), where features include air volume (load), engine speed, torque, and VVT accuracy.

[0121] 1) If Cnt N Less than At that time, = ; Similarly, it is stored in the EEPROM after the vehicle is powered off. Updated under the same working conditions last time Its initial default value is 0;

[0122] 2) Once Cnt N = ,but = And Cnt N Reset to 0, where f is 0.002 in this instance, and f is the update iteration coefficient.

[0123] Final VVT minimum phase learning coefficients It is limited to between -0.5 and 0.5.

[0124] The minimum phase learning value of VVT after being constrained The corresponding operating condition is stored in the EEPROM.

[0125] Calculate the final VVT minimum phase Then the final VVT minimum phase When the VVT ​​target phase is lower than its minimum VVT phase, the VVT ​​control system is shut down, meaning VVT activation is not allowed. This serves as the minimum limit for setting the VVT ​​target phase, preventing power and emission issues caused by setting the target too low during the VVT ​​target setting process.

[0126] See Figure 5 The present invention provides a VVT minimum target phase control device, comprising the following steps:

[0127] Determine the minimum phase of the basic VVT Module: Basic VVT Minimum Phase The calibration results were obtained from engine bench calibration. The calibration was based on the following: when the catalytic converter ignition was complete and the coolant temperature was at warm-up temperature, the VVT ​​was activated and the target VVT phase was reduced. The difference in fuel consumption between the initial value of the minimum VVT phase and the value when the VVT ​​phase was 0 was compared to determine the basic minimum VVT phase. ;

[0128] Determine the minimum phase of the original VVT Module: Minimum phase of basic VVT Corrections are made under various vehicle operating conditions to obtain the original VVT minimum phase of the entire vehicle. ;

[0129] VVT Minimum Phase Self-Learning Module: When the engine operating conditions are stable, VVT minimum phase self-learning is performed. Under the premise that the VVT ​​minimum phase self-learning activation conditions are met, it sequentially enters the VVT ​​minimum phase self-learning stabilization stage, VVT minimum phase self-learning activation stage, VVT minimum phase self-learning update stage, and VVT minimum phase self-learning storage stage, storing the VVT ​​minimum phase learning coefficients for each operating condition. All values ​​are stored in the EEPROM and corrected to obtain the final minimum phase of VVT. .

[0130] The key points and technical principles of this invention are as follows:

[0131] 1) The original minimum phase of VVT determined for the whole vehicle.

[0132] 2) VVT minimum phase self-learning activation condition.

[0133] 3) VVT minimum phase learning and update method.

[0134] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0135] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A method for VVT minimum target phase control, characterized in that: Includes the following steps: Determine the minimum phase of the basic VVT Minimum phase of basic VVT The calibration results were obtained from engine bench calibration. The calibration was based on the following: when the catalytic converter ignition was complete and the coolant temperature was at warm-up temperature, the VVT ​​was activated and the target VVT phase was reduced. The difference in fuel consumption between the initial value of the minimum VVT phase and the value when the VVT ​​phase was 0 was compared to determine the basic minimum VVT phase. ; Determine the minimum phase of the original VVT : Minimum phase of the basic VVT Corrections are made under various vehicle operating conditions to obtain the original VVT minimum phase of the entire vehicle. ; VVT Minimum Phase Self-Learning: When the engine operating conditions are stable, VVT minimum phase self-learning is performed. Under the premise that the VVT ​​minimum phase self-learning activation conditions are met, it sequentially enters the VVT ​​minimum phase self-learning stabilization stage, VVT minimum phase self-learning activation stage, VVT minimum phase self-learning update stage, and VVT minimum phase self-learning storage stage, storing the VVT ​​minimum phase learning coefficients for each operating condition. All values ​​are stored in the EEPROM and corrected to obtain the final minimum phase of VVT. , in, The activation conditions for VVT minimum phase self-learning are as follows: Engine running time: The engine is running and the engine running time exceeds the first preset time; Closed-loop control: The VVT ​​system is in a closed-loop control active state; Preset phase difference: Current VVT target phase The difference between the minimum phase and VVT does not exceed a preset range; Carbon canister: The carbon canister is not opened; Cylinder intake density: The target fresh air intake density entering the cylinder is within a certain range, and the fluctuation of the target fresh air intake density entering the cylinder during the self-learning of the minimum phase of VVT is small, taken as ±10mgpl. Engine coolant temperature fluctuation: The engine coolant temperature fluctuation is small within a certain range and enters the VVT ​​minimum phase self-learning stage. It is taken as ±2℃. Intake temperature fluctuation: The intake temperature fluctuation is small within a certain range and when entering the minimum phase of VVT self-learning, it is taken as ±1.5℃. Oil temperature fluctuation: The oil temperature fluctuation is small within a certain range and when the self-learning process of entering the minimum phase of VVT is completed, it is taken as ±1.5℃. Oil pressure fluctuation: The oil pressure fluctuation is small within a certain range and enters the VVT ​​minimum phase self-learning stage, which is ±5kPa. Engine speed closed-loop control: Engine speed enters closed-loop control; Engine target speed fluctuation: The engine target speed is within a certain range, and the engine target speed fluctuation is small when entering the VVT ​​minimum phase self-learning, which is ±5 rpm; Crankshaft forced ventilation on / off status: The crankshaft forced ventilation function remains unchanged. Detonation or pre-ignition: No detonation or pre-ignition occurred; Intake density fluctuation: The intake density fluctuation of the fresh air entering the cylinder is small, taken as ±10mgpl; The specific process of the VVT ​​minimum phase self-learning stabilization stage is as follows: Second preset time T0 judgment: Determine whether the entry into the VVT ​​minimum phase self-learning stabilization stage exceeds the second preset time T0; Third preset time T1 judgment: Determine whether the self-learning no-update time interval of the minimum phase of VVT exceeds the third preset time T1; Maintain the current stage: If the conditions for the second preset time T0 and the third preset time T1 are not met, but the activation condition is met, then the system remains in the VVT ​​minimum phase self-learning stabilization stage. Return to the previous stage: If the conditions for the second preset time T0 and the third preset time T1 are not met, and the activation condition is not met, then re-evaluate whether the VVT ​​minimum phase self-learning activation condition is met. Proceed to the next stage: If the conditions for the second preset time T0 and the third preset time T1 are met, and the activation condition is also met, then proceed to the VVT ​​minimum phase self-learning activation stage. The specific process of the VVT ​​minimum phase self-learning activation phase is as follows: During the self-learning activation phase of VVT minimum phase, the following parameters are cumulatively calculated within the cumulative time T2: total engine speed, total intake air temperature, total coolant temperature, total oil temperature, total oil pressure, total target intake air density, total actual intake air density, and total target engine speed. Total and actual engine speed filtering Total value, target engine fire circuit torque Total, actual engine firing torque Once the sum of the VVT ​​target phase and the sum of the VVT ​​actual phase are satisfied within the cumulative time T2, the VVT ​​minimum phase self-learning update phase begins. The specific process of the VVT ​​minimum phase self-learning update phase is as follows: When the intake air temperature, coolant temperature, oil temperature, oil pressure, engine target speed, target fresh air intake density, and VVT target phase are the same as the aforementioned parameters, the same operating condition is defined; the minimum phase learning coefficient of VVT under each operating condition is set. All are stored in EEPROM.

2. The VVT ​​minimum target phase control method according to claim 1, characterized in that: In the VVT ​​minimum phase self-learning activation phase of the VVT ​​minimum phase self-learning step, the actual engine speed is filtered. The value is calculated as follows: in, This is the original value of the actual engine speed. This represents the original value of the actual engine speed during the Nth sampling period. This is the actual engine speed filtered value after first-order low-pass filtering. This is the filtered value of the actual engine speed in the Nth sampling period. This represents the filtered value of the actual engine speed in the (N-1)th sampling period, where N = 1, 2, 3… The original value of the actual engine speed at the moment of entering the self-learning activation phase. , The coefficient is the engine speed filter coefficient.

3. The VVT ​​minimum target phase control method according to claim 2, characterized in that: The specific process of the VVT ​​minimum phase self-learning storage stage in the VVT ​​minimum phase self-learning step is as follows: Average value calculation: Calculate the average intake air temperature, average coolant temperature, average engine oil temperature, average engine oil pressure, and average engine target speed during the cumulative time T2 segment within the VVT ​​minimum phase self-learning phase. Average value of actual engine speed filter The average density of fresh air entering the cylinder. Average density of fresh air entering the cylinder Target engine fire circuit average torque Actual engine firing average torque VVT target phase average value , VVT actual phase average ; Operating condition update: Update the average intake air temperature to the corresponding intake air temperature operating condition, update the average coolant temperature to the corresponding coolant temperature operating condition, update the average oil temperature to the corresponding oil temperature operating condition, update the average oil pressure to the corresponding oil pressure operating condition, update the average engine target speed to the corresponding engine target speed operating condition, update the learned value of the target intake air density into the cylinder to the corresponding target intake air density into the cylinder operating condition, update the learned value of the VVT ​​target phase operating condition to the corresponding VVT target phase operating condition, and store each updated value in the EEPROM.

4. The VVT ​​minimum target phase control method according to claim 3, characterized in that: The specific process of the operating condition update step in the VVT ​​minimum phase self-learning step, specifically the VVT ​​minimum phase self-learning storage stage, is as follows: VVT minimum phase learning value Correction method: ， ， ， ， Level Classification: Based on the aforementioned formula, C1 is determined as the minimum target phase correction coefficient for VVT based on gas volume. C1 is divided into four levels, see Table 1: Table 1 Based on the aforementioned formula, C2 is determined to be the minimum target phase correction coefficient for VVT based on rotational speed. C2 is divided into four levels, see Table 2: Table 2 Based on the aforementioned formula, C3 is determined to be the minimum target phase correction coefficient for torque-based VVT. C3 is divided into six levels, see Table 3: Table 3 Based on the aforementioned formula, C4 is determined to be the minimum target phase correction coefficient for VVT based on VVT control accuracy. C4 is divided into seven levels, see Table 4: Table 4 Calculate the minimum phase learning coefficients for VVT When C1, C2, C3, and C4 meet the corresponding levels, the number of phase learning updates corresponds to Cnt. N Add 1, Cnt during each learning process N If VVT minimum phase learning is performed only once, and at most once in each driving cycle, then the final VVT minimum phase learning coefficients are... : ,in, The minimum phase learning coefficient of VVT learned under the same operating conditions in the previous operation; ， in, Initial values ​​of VVT minimum phase learning coefficients This represents the maximum number of updates. The minimum target phase correction coefficient for VVT is defined based on various features, where N = 1, 2, 3, 4, and the features include load, engine speed, torque, and VVT accuracy. , , , ,in, The minimum target phase correction coefficient for VVT is defined based on various features, where N = 1, 2, 3, 4, and the features include load, engine speed, torque, and VVT accuracy. If Cnt N Less than At that time, = ; The data will be stored in the EEPROM after the vehicle is powered off. Updated under the same working conditions last time The initial default value is 0; Once Cnt N = ,but = And Cnt N Reset to 0, where f is the update iteration coefficient; The minimum phase learning coefficients of VVT that are ultimately learned after being restricted Stored in the corresponding operating condition of EEPROM. Calculate the final VVT minimum phase Then the minimum phase of the final VVT is obtained. When the target phase of VVT is lower than the minimum phase of the final VVT At this time, the VVT ​​control system is turned off, that is, VVT activation is not allowed, and the final VVT minimum phase is turned off. This serves as the minimum limit when setting the target phase for VVT.

5. The VVT ​​minimum target phase control method according to claim 4, characterized in that: The determination of the original VVT minimum phase The specific steps are as follows: First multiplication factor: Determined based on real-time atmospheric pressure and real-time oil temperature. ; Second multiplication factor: Determined based on engine combustion cycles and atmospheric temperature. ; Third multiplication factor: Determined based on real-time coolant temperature and engine starting coolant temperature. ; Fourth multiplication factor: Determined based on real-time water temperature and intake air temperature. ; Fifth multiplication factor: Determined based on the mass flow rate of fuel vapor entering the cylinder from the carbon canister and the engine speed. ; The sixth multiplication factor is determined based on the oil pressure and the rate of change of oil pressure. ; Seventh multiplication factor: Determine the seventh multiplication factor based on the crankshaft forced ventilation function's on / off status. ; Eighth multiplication factor: based on engine speed and load fluctuation coefficient Determine the eighth multiplication factor , Among them, load fluctuation coefficient The method for determining it is as follows: in, This refers to the actual fresh air intake density entering the cylinder. This represents the actual fresh air intake density entering the cylinder during the Nth sampling period. This represents the actual fresh air intake density entering the cylinder after a first-order low-pass filter. This represents the filtered actual fresh air intake density entering the cylinder during the Nth sampling period. The filtered actual fresh air intake density entering the cylinder during the (N-1)th sampling period, where N = 1, 2, 3… This equals the actual fresh air intake density entering the cylinders immediately after the engine has successfully started. , Load fluctuation filter coefficients: ,in The number of engine cylinders. Engine speed, This refers to the gas volume filtering coefficient; Load fluctuation coefficient The original VVT minimum phase of the whole vehicle : 。 6. A VVT minimum target phase control device, comprising a computer program, characterized in that: The computer program is capable of executing the VVT ​​minimum target phase control method as described in claims 1 to 5.

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