A clutch half-engagement point self-learning method of a wet DCT

Abstract

A clutch half-coupling point self-learning method of a wet DCT, comprising the following steps: 1) obtaining a pressure-current theoretical relationship curve of a clutch electromagnetic valve; 2) taking the pressure value corresponding to the maximum theoretical half-coupling point of clutch hardware design as the oil filling pressure value of the clutch, and taking the current value corresponding to the oil filling pressure value as the oil filling current value; 3) taking the minimum value of the clutch piston movement pressure point as the self-learning pressure value, and taking the current value corresponding to the self-learning pressure value as the self-learning current value; 4) adjusting the input current of the electromagnetic valve according to the oil filling current value and the self-learning current value by a fixed step size, obtaining the theoretical pressure value of the clutch corresponding to different input currents of the electromagnetic valve by using the pressure-current theoretical relationship curve, calculating the difference between each clutch theoretical pressure value and the corresponding clutch actual pressure value, and adjusting the half-coupling point pressure setting value of the clutch of the TCU in real time according to the clutch actual pressure value when the difference is maximum.

Description

Technical Field

[0001] This invention relates to the field of DCT control, and specifically to a self-learning method for the clutch half-engagement point of a wet DCT. Background Technology

[0002] A wet dual-clutch transmission (DCT) is a type of dual-clutch transmission that uses hydraulic fluid to cool the clutches. In vehicles using this type of transmission, the hydraulic system or electric motor drives the disengagement and engagement of two clutches during gear shifts, achieving uninterrupted power transmission. It combines the advantages of manual and automatic transmissions, improving fuel economy and ensuring smooth gear shifts. It is widely used by major automobile manufacturers in China. The hydraulic system, as the driving force for clutch disengagement and engagement, directly affects the comfort of the dual-clutch transmission's shifting performance due to the quality of clutch pressure control.

[0003] Current clutch pressure control solutions typically calculate the desired torque for each of the two clutches based on the vehicle's power requirements and torque conditions. The next step is to interpolate the desired torque using the torque-pressure characteristic curve to obtain the desired output pressure. Then, the desired output pressure is interpolated using the pressure-current characteristic curve to obtain the target current. Finally, the target current is input to the solenoid valve to control the clutch piston chamber engagement pressure, thereby achieving the clutch engagement and disengagement actions.

[0004] To achieve smooth clutch control during this process, a pressure sensor is typically installed at the clutch end. The pressure signal collected by the sensor is used as a feedback signal to adjust the desired output pressure, resulting in the final output control pressure. However, pressure sensors are often affected by various factors during use, such as temperature, fluid quality, and clutch wear. This causes the actual half-engagement point data of the wet DCT to change continuously throughout the entire lifespan of the wet DCT, resulting in errors compared to the clutch half-engagement point data stored in the TCU. The magnitude of this error directly affects the quality of clutch pressure control. If this error cannot be controlled within the allowable range in a timely manner, it can easily cause shift shocks or shift jerks during driving, leading to performance problems and safety hazards.

[0005] Conventional self-learning methods for clutch half-engagement points have always been sensitive to pressure fluctuations, leading to significant learning errors. While the publication CN115654034A, titled "Self-Learning Method for Half-Engagement Point of Hydraulic Wet Clutch," filters clutch pressure during the self-learning process to eliminate the influence of external factors such as pressure fluctuations, this also complicates the entire self-learning process, hindering the accurate acquisition of clutch half-engagement point data.

[0006] How to simplify the self-learning process as much as possible while ensuring that the results of self-learning are within the allowable error range, under the condition of eliminating a series of external factors such as pressure fluctuations, has always been an urgent problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a self-learning method for the clutch half-engagement point of a wet DCT. This method greatly simplifies the self-learning process of the clutch half-engagement point by eliminating external factors such as pressure fluctuations. It learns and updates the clutch half-engagement point pressure value in real time as various factors such as temperature, fluid quality, and clutch wear change, ensuring that the error between the clutch half-engagement point data stored in the TCU and the actual half-engagement point data of the wet DCT is within an acceptable range. This avoids performance or functional problems such as shift shock and shift jerking during vehicle operation, preventing safety hazards.

[0008] The objective of this invention is achieved through the following solution: a self-learning method for the clutch half-engagement point of a wet DCT, comprising the following steps: 1) Obtain the theoretical pressure-current relationship curve of the clutch solenoid valve; 2) The pressure value corresponding to the maximum theoretical half-engagement point of the clutch hardware design is taken as the clutch filling pressure value, and the current value corresponding to the filling pressure value is taken as the filling current value. 3) Take the minimum value of the clutch piston movement pressure point as the self-learning pressure value, and take the current value corresponding to the self-learning pressure value as the self-learning current value. 4) The clutch half-engagement point self-learning function is triggered based on the transmission oil temperature. Then, the input current of the solenoid valve is adjusted according to the oil filling current value and the self-learning current value in a fixed step size. The theoretical pressure value of the clutch corresponding to different solenoid valve input currents is obtained by using the pressure-current theoretical relationship curve. The difference between the theoretical pressure value of each clutch and the actual pressure value of the corresponding clutch is calculated. The clutch half-engagement point pressure setting value of the TCU is adjusted in real time according to the actual pressure value of the clutch when the difference is the largest.

[0009] Preferably, the method for adjusting the clutch half-engagement point pressure setting value of the TCU in real time includes the following steps: 4-1) Clutch filling stage: Adjust the input current of the wet DCT solenoid valve to match the oil filling current value, and compare the actual clutch pressure value with the clutch oil filling pressure value: If the actual clutch pressure value is less than the clutch filling pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is greater than or equal to the clutch oil filling pressure value, then the clutch enters the self-learning stage of the half-engagement point. 4-2) Clutch half-engagement point self-learning stage: Adjust the input current of the wet DCT solenoid valve to the self-learning current value, and compare the actual clutch pressure value with the self-learning pressure value: If the actual clutch pressure value is greater than the self-learning pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is less than or equal to the self-learning pressure value, then the clutch half-engagement point self-learning will be performed in the following manner: ① Increase the input current of the wet DCT solenoid valve by a fixed step size; ② Obtain the theoretical clutch pressure value corresponding to the current input current of the wet DCT solenoid valve based on the theoretical relationship curve; ③ Record the difference between the theoretical clutch pressure value corresponding to the current wet DCT solenoid valve input current and the current actual clutch pressure value, as the pressure difference data; ④ Repeat steps ① to ③ until the actual clutch pressure value is greater than the clutch filling pressure value, and adjust the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is the largest.

[0010] Preferably, a preset number of self-learning repetitions is used to repeat step 4-2) multiple times to perform clutch half-engagement point self-learning. The actual clutch pressure value at the time when the pressure difference data is the largest in each clutch half-engagement point self-learning stage is recorded. The average value of these actual clutch pressure values ​​is calculated, and the original clutch half-engagement point pressure value in the transmission TCU is modified according to the average value.

[0011] Preferably, when the number of self-learning repetitions is greater than 1, a fluctuation threshold for the self-learning result of the half-engagement point is set, and the original clutch half-engagement point pressure value in the transmission TCU is modified in the following manner: (1) Determine whether the actual clutch pressure value at the point where the pressure difference recorded during the self-learning phase of each clutch half-engagement point is the largest is valid: Calculate the difference between the actual clutch pressure value when the current recorded pressure difference data is the largest and the actual clutch pressure value when the previous recorded pressure difference data is the largest. If the difference is less than the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is valid. If the difference is greater than or equal to the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is invalid. (2) Eliminate invalid clutch actual pressure values, add up all valid clutch actual pressure values, calculate the average value, and modify the original clutch half-engagement point pressure value in the transmission TCU according to the average value.

[0012] Preferably, in step ④, before modifying the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is at its maximum, the temperature compensation value corresponding to the current transmission oil temperature is first queried in the temperature compensation table, and then the actual clutch pressure value when the pressure difference data is at its maximum is added to the queried temperature compensation value. Finally, the obtained sum is used to modify the original clutch half-engagement point pressure value in the transmission TCU.

[0013] Preferably, before modifying the original clutch half-engagement pressure value in the transmission TCU according to the average value, the temperature compensation value corresponding to the current transmission oil temperature is first queried in the temperature compensation table, then the average value is added to the queried temperature compensation value, and finally the obtained sum is used to modify the original clutch half-engagement pressure value in the transmission TCU.

[0014] Preferably, the temperature compensation gauge is obtained through a calibration experiment.

[0015] The advantages of this invention are as follows: ① This invention can learn and update the clutch half-engagement point pressure value in real time as various factors such as temperature, oil quality and clutch wear change, ensuring that the error between the clutch half-engagement point data stored in the TCU and the actual half-engagement point data of the wet DCT clutch is within the allowable range, avoiding performance problems such as shift shock or shift jerking during vehicle operation, and avoiding safety hazards. ② Compared with the "Self-learning method for the half-engagement point of a hydraulic wet clutch" published in CN115654034A, the present invention has lower sensitivity to pressure fluctuations, does not require filtering, and the self-learning process of the half-engagement point is simpler. Attached Figure Description

[0016] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the curves related to the self-learning process of the clutch half-engagement point of the wet DCT in an embodiment of the present invention. Detailed Implementation

[0017] like Figures 1 to 2 As shown, the objective of this invention is achieved through the following solution: a self-learning method for the clutch half-engagement point of a wet DCT, comprising the following steps: 1) Obtain the theoretical pressure-current relationship curve of the clutch solenoid valve; The pressure-current theoretical relationship curve in this embodiment is actually the fitted relationship curve between the input current of the solenoid valve and the corresponding output pressure. It is usually obtained through calibration tests before the clutch solenoid valve leaves the factory and is usually provided by the solenoid valve manufacturer.

[0018] 2) The pressure value corresponding to the maximum theoretical half-engagement point of the clutch hardware design is taken as the clutch filling pressure value, and the current value corresponding to the filling pressure value is taken as the filling current value. The maximum theoretical half-engagement point of the clutch hardware design is usually provided by the clutch manufacturer. The half-engagement point with the highest pressure value within the theoretical distribution range of the clutch's half-engagement points can be taken as the maximum theoretical half-engagement point of the clutch hardware design. The theoretical distribution range of the clutch's half-engagement points can generally be calculated using the clutch design's dimensional chain and the clutch's torque transmission characteristics during engagement.

[0019] 3) Take the minimum value of the clutch piston movement pressure point as the self-learning pressure value, and take the current value corresponding to the self-learning pressure value as the self-learning current value. In this embodiment, the self-learning pressure value is greater than the elastic force of the piston return spring plus the static friction force between the piston and the piston cylinder, and is infinitely close to the sum of the elastic force of the piston return spring and the static friction force between the piston and the piston cylinder. Essentially, this ensures that once the pressure on the piston, which is stationary in the cylinder, reaches the minimum pressure point for clutch piston movement, it will transition from a stationary state to a moving state. This minimum pressure point for clutch piston movement can also be provided by the clutch design manufacturer.

[0020] 4) The clutch half-engagement point self-learning function is triggered based on the transmission oil temperature. Then, the input current of the solenoid valve is adjusted according to the oil filling current value and the self-learning current value in fixed steps. The theoretical clutch pressure value corresponding to different solenoid valve input currents is obtained using the pressure-current theoretical relationship curve. The difference between the theoretical pressure value and the actual pressure value of each clutch is calculated. The clutch half-engagement point pressure setting value of the TCU is adjusted in real time according to the actual clutch pressure value when the difference is the largest. The specific steps are as follows: 4-1) Clutch filling stage: Adjust the input current of the wet DCT solenoid valve to match the oil filling current value, and compare the actual clutch pressure value with the clutch oil filling pressure value: If the actual clutch pressure value is less than the clutch filling pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is greater than or equal to the clutch oil filling pressure value, then the clutch enters the self-learning stage of the half-engagement point. 4-2) Clutch half-engagement point self-learning stage: Adjust the input current of the wet DCT solenoid valve to the self-learning current value, and compare the actual clutch pressure value with the self-learning pressure value: If the actual clutch pressure value is greater than the self-learning pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is less than or equal to the self-learning pressure value, then the clutch half-engagement point self-learning will be performed in the following manner: ① Increase the input current of the wet DCT solenoid valve by a fixed step size; ② Obtain the theoretical clutch pressure value corresponding to the current input current of the wet DCT solenoid valve based on the theoretical relationship curve; ③ Record the difference between the theoretical clutch pressure value corresponding to the current wet DCT solenoid valve input current and the current actual clutch pressure value, as the pressure difference data; ④ Repeat steps ① to ③ until the actual clutch pressure value is greater than the clutch filling pressure value, and adjust the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is the largest.

[0021] In step ④ of this embodiment, before modifying the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is at its maximum, the temperature compensation value corresponding to the current transmission oil temperature is first queried in the temperature compensation table. Then, the actual clutch pressure value when the pressure difference data is at its maximum is added to the queried temperature compensation value. Finally, the obtained sum is used to modify the original clutch half-engagement point pressure value in the transmission TCU.

[0022] To ensure the effectiveness of self-learning and keep the error within an acceptable range, this embodiment pre-sets the self-learning repetition to be 3 times, that is, this embodiment repeats step 4-2) three times to perform three clutch half-engagement point self-learnings. The actual clutch pressure values ​​P(t1), P(t2), and P(t3) when the pressure difference data is the largest in the three clutch half-engagement point self-learning stages are recorded respectively. After determining whether the actual clutch pressure value when the pressure difference data is the largest in each clutch half-engagement point self-learning stage is valid, all valid clutch actual pressure values ​​are added together and the average value is calculated. The original clutch half-engagement point pressure value in the transmission TCU is modified according to the average value.

[0023] If the results of three and a half binding point self-learning sessions are all invalid, then three more and a half binding point self-learning sessions will be performed until at least one of the half binding point self-learning sessions is valid.

[0024] In this embodiment, the method for determining the validity of the actual clutch pressure value when the pressure difference data recorded during the self-learning phase of each clutch half-engagement point is the largest is as follows: Calculate the difference between the actual clutch pressure value when the current recorded pressure difference data is the largest and the actual clutch pressure value when the previous recorded pressure difference data is the largest. If the difference is less than the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is valid. If the difference is greater than or equal to the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is invalid. It is worth noting that before modifying the original clutch half-engagement pressure value in the transmission TCU according to the average value, the temperature compensation value corresponding to the current transmission oil temperature should be looked up in the temperature compensation table obtained by the calibration experiment in advance. Then, the average value is added to the temperature compensation value found. Finally, the original clutch half-engagement pressure value in the transmission TCU is modified using the sum. This can better control the error of the self-learning result affected by temperature within the allowable range.

[0025] To ensure the safety of the entire self-learning process, before triggering the clutch half-engagement point self-learning function, it should be determined whether the current state of the vehicle meets the preparatory conditions for triggering the clutch half-engagement point self-learning function. Then, the current transmission oil temperature is compared with the oil temperature threshold. If the transmission oil temperature is ≥ the oil temperature threshold, the clutch half-engagement point self-learning function is triggered. If the transmission oil temperature is < the oil temperature threshold, the clutch half-engagement point self-learning function is not triggered (the oil temperature threshold setting depends on the specific situation, and can usually be set to 60℃).

[0026] In this embodiment, when the vehicle is in a parked idling state, the preparatory conditions for triggering the clutch half-engagement point self-learning function are as follows: (1) The current vehicle speed is zero; (2) Confirm that the handbrake is engaged; (3) The gear position is in neutral; When the car is in a parked idling state, all three conditions mentioned above must be met simultaneously; none can be omitted. This allows for simultaneous self-learning of the half-engagement point of both clutches in a wet DCT.

[0027] When the car is in motion, it is necessary to first determine whether the current DCT transmission gear is an odd or even gear. If the current gear is an odd gear, the following preconditions must be met simultaneously before the clutch corresponding to the even gear can perform self-learning of the half-engagement point: (1) Engine speed > engine speed threshold (the setting of the engine speed threshold depends on the specific situation, and can usually be set to 2000 rpm). (2) Accelerator pedal change rate ≤ accelerator pedal change rate threshold (the accelerator pedal change rate threshold is set according to the specific situation, and can usually be set to 5%). (3) The even-numbered synchronizer fork returns to the neutral position.

[0028] Similarly, when the car is in a driving state, if the current gear is an even gear, and if the above two preparatory conditions are met at the same time, the clutch corresponding to the odd gear can also perform self-learning of the half-engagement point.

[0029] In summary, when the clutch half-engagement point self-learning function is triggered under driving conditions to correct the clutch half-engagement point, it is necessary to ensure that the clutch self-learning process does not affect the torque transmission of the transmission during normal driving.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A self-learning method for the clutch half-engagement point of a wet DCT, characterized in that, Includes the following steps: 1) Obtain the theoretical pressure-current relationship curve of the clutch solenoid valve; 2) Obtain the pressure value corresponding to the maximum theoretical half-engagement point of the clutch hardware design as the clutch filling pressure value, and use the current value corresponding to the filling pressure value as the filling current value. 3) Obtain the minimum value of the clutch piston movement pressure point as the self-learning pressure value, and use the current value corresponding to the self-learning pressure value as the self-learning current value. 4) The clutch half-engagement point self-learning function is triggered based on the transmission oil temperature. Then, the input current of the solenoid valve is adjusted according to the oil filling current value and the self-learning current value in a fixed step size. The theoretical pressure value of the clutch corresponding to different solenoid valve input currents is obtained by using the pressure-current theoretical relationship curve. The difference between the theoretical pressure value of each clutch and the actual pressure value of the corresponding clutch is calculated. The clutch half-engagement point pressure setting value of the TCU is adjusted in real time according to the actual pressure value of the clutch when the difference is the largest.

2. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 1, characterized in that, The method for adjusting the clutch half-engagement point pressure setting of the TCU in real time includes the following steps: 4-1) Clutch filling stage: Adjust the input current of the wet DCT solenoid valve to match the oil filling current value, and compare the actual clutch pressure value with the clutch oil filling pressure value: If the actual clutch pressure value is less than the clutch filling pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is greater than or equal to the clutch filling pressure value, then the clutch enters the self-learning stage of the half-engagement point. 4-2) Clutch half-engagement point self-learning stage: Adjust the input current of the wet DCT solenoid valve to the self-learning current value, and compare the actual clutch pressure value with the self-learning pressure value: If the actual clutch pressure value is greater than the self-learning pressure value, then the input current of the solenoid valve will continue to be maintained. If the actual clutch pressure value is less than or equal to the self-learning pressure value, then the clutch half-engagement point self-learning will be performed in the following manner: ① Increase the input current of the wet DCT solenoid valve by a fixed step size; ② Obtain the theoretical clutch pressure value corresponding to the current input current of the wet DCT solenoid valve based on the theoretical relationship curve; ③ Record the difference between the theoretical clutch pressure value corresponding to the current wet DCT solenoid valve input current and the current actual clutch pressure value, as the pressure difference data; ④ Repeat steps ① to ③ until the actual clutch pressure value is greater than the clutch filling pressure value, and adjust the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is the largest.

3. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 2, characterized in that, Set the preset number of self-learning repetitions, and repeat step 4-2) multiple times according to the preset number of self-learning repetitions to perform clutch half-engagement point self-learning. Record the actual clutch pressure value when the pressure difference data is the largest in each clutch half-engagement point self-learning stage, calculate the average value of these actual clutch pressure values, and modify the original clutch half-engagement point pressure value in the transmission TCU according to the average value.

4. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 3, characterized in that, When the number of self-learning repetitions is greater than 1, set a threshold for the fluctuation of the half-engagement point self-learning result, and modify the original clutch half-engagement point pressure value in the transmission TCU as follows: (1) Determine whether the actual clutch pressure value at the point where the pressure difference recorded during the self-learning phase of each clutch half-engagement point is the largest is valid: Calculate the difference between the actual clutch pressure value when the current recorded pressure difference data is the largest and the actual clutch pressure value when the previous recorded pressure difference data is the largest. If the difference is less than the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is valid. If the difference is greater than or equal to the fluctuation threshold of the half-engagement point self-learning result, the actual clutch pressure value when the current recorded pressure difference data is the largest is invalid. (2) Eliminate invalid clutch actual pressure values, add up all valid clutch actual pressure values, calculate the average value, and modify the original clutch half-engagement point pressure value in the transmission TCU according to the average value.

5. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 2, characterized in that, In step ④, before modifying the original clutch half-engagement point pressure value in the transmission TCU according to the actual clutch pressure value when the pressure difference data is at its maximum, first look up the temperature compensation value corresponding to the current transmission oil temperature in the temperature compensation table, then add the actual clutch pressure value when the pressure difference data is at its maximum to the queried temperature compensation value, and finally use the sum to modify the original clutch half-engagement point pressure value in the transmission TCU.

6. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 3 or 4, characterized in that, Before modifying the original clutch half-engagement pressure value in the transmission TCU based on the average value, first look up the temperature compensation value corresponding to the current transmission oil temperature in the temperature compensation table, then add the average value to the looked-up temperature compensation value, and finally use the sum to modify the original clutch half-engagement pressure value in the transmission TCU.

7. The self-learning method for the clutch half-engagement point of a wet DCT according to claim 5, characterized in that, The temperature compensation table was obtained through calibration experiments.

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