Clutch pre-separation method for power downshift of vehicle automatic transmission

Abstract

The invention belongs to the technical field of traditional automobiles, and particularly relates to a clutch pre-separation method for power downshift of an automatic transmission of a vehicle, which comprises the following steps: S1, acquiring state data of the vehicle; s2, predicting whether power downshift occurs or not; if so, turning to S3; otherwise, returning to S1; s3, the clutch is controlled to execute torque reduction according to the preset torque slope, and clutch separation is conducted; a closed-loop control strategy is used in the clutch separation process, and the rotating speed difference between the engine and the input shaft is controlled to change towards the target rotating speed difference; s4, if a downshift instruction is received within a preset duration after the pre-division strategy is started to be executed, turning to S5; if not, turning to S6; and S5, the pre-division strategy is ended, the downshift control operation is executed, and after the downshift control operation is completed and the normal driving state is recovered, the step S1 is executed again. And S6, recombining the clutch, and returning to S1 after the normal driving state is recovered. According to the method, gear shifting smoothness and response speed can be improved, and meanwhile abrasion of mechanical parts is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of traditional automobile technology, and in particular relates to a clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle. Background Art

[0002] In traditional automotive applications, the automatic transmission (AT), a crucial component of the vehicle's powertrain, automatically adjusts the gear based on parameters such as vehicle speed and engine load, thereby optimizing the vehicle's power output and fuel economy. Power downshifting is the process by which the automatic transmission shifts from a higher gear to a lower gear when the vehicle requires more torque, such as when accelerating, overtaking, or climbing a hill. This process is crucial for enhancing the driving experience and ensuring driving safety.

[0003] However, in the existing technology, automatic transmissions face some challenges when performing power downshifts. First, traditional downshift strategies often ignore the impact of factors such as throttle opening and change rate on the timing of gear shifting, resulting in untimely or too frequent gear shifting, affecting driving smoothness and response speed. Secondly, directly downshifting may cause the speed difference between the engine speed and the transmission input shaft to be too large, resulting in a large mechanical shock, which not only reduces ride comfort but also may shorten the service life of the transmission. In addition, how to achieve a smooth gear shift transition while ensuring a fast response is also a technical problem that needs to be solved urgently. Existing control strategies usually rely on fixed shift points, which are difficult to adapt to complex driving conditions and different driving styles of drivers.

[0004] Therefore, how to improve the smoothness and response speed of gear shifting, reduce the wear of mechanical components, and enhance the vehicle's safety performance and driving experience has become an urgent problem to be solved. Summary of the Invention

[0005] In response to the above-mentioned deficiencies in the prior art, the present invention provides a clutch pre-disengagement method for power downshifting of a vehicle automatic transmission, which can improve the smoothness and response speed of gear shifting, while reducing the wear of mechanical components and enhancing the vehicle's safety performance and driving experience.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle comprises the following steps: S1. Acquire vehicle status data while the vehicle is traveling; S2. Predict whether a power downshift will occur based on the acquired status data; if the prediction result is that a power downshift may occur, proceed to S3; otherwise, return to S1 to reacquire status data; S3: Executing a pre-disengagement strategy to control the clutch to reduce torque according to a preset torque slope, thereby disengaging the clutch; and using a closed-loop control strategy during the clutch disengagement process to control the speed difference between the engine and the input shaft toward the target speed difference; S4: If a downshift command is received within a preset time after the pre-shift strategy is started, go to S5; if not, go to S6; S5. End the pre-shift strategy, execute the downshift control operation, and after completing the downshift control operation and restoring the normal driving state, return to S1.

[0007] S6. Reengage the clutch and return to S1 after returning to normal driving state.

[0008] Compared with the prior art, the present invention has the following beneficial effects: 1. During vehicle movement, this method acquires real-time vehicle status data (such as transmission status, throttle opening and rate of change), predicts whether a power downshift will occur based on this data, and executes the corresponding action based on the prediction. Compared to existing methods that rely on fixed shift points, this method can more accurately identify driver intent and respond in advance. Traditional methods often only initiate downshifts when a downshift is actually required, while this invention can prepare for it immediately when a downshift is predicted, significantly improving response speed and accuracy.

[0009] 2. When a power downshift is predicted, this method implements a pre-shift strategy, preemptively increasing engine speed and pre-disengaging the clutch before a power downshift command is issued, saving time for the subsequent power downshift. This process not only speeds up downshifts but also avoids engine roar caused by sudden acceleration, improving ride comfort. Compared to the delay and potential noise issues associated with direct downshifts, this method ensures a smoother and quieter downshift by pre-adjusting engine speed.

[0010] 3. A closed-loop control strategy manages clutch disengagement and engagement, ensuring the speed differential between the engine and input shaft remains within the target range. This closed-loop control system dynamically adjusts engine torque or clutch engagement force based on the measured speed differential, precisely controlling power delivery and avoiding mechanical shock caused by speed mismatch. The closed-loop control strategy monitors and adjusts the speed differential between the engine and input shaft in real time, keeping them as close to the preset target speed differential as possible. This significantly reduces shift shock, resulting in smoother shifts and improved driving comfort. Furthermore, closed-loop control continuously corrects errors through a continuous feedback mechanism, ensuring the speed differential between the engine and input shaft always approaches the ideal value, improving overall system responsiveness. Compared to open-loop control, closed-loop control can more quickly respond to changes and make appropriate adjustments. This means that when a power downshift is detected, the system can react quickly, ensuring fast and accurate shifts.

[0011] 4. If a downshift command is received within a preset time after the pre-shift strategy begins, the downshift control operation will be executed. If no downshift command is received (i.e., no power downshift occurs subsequently), the method will re-engage the clutch and resume normal driving. This configuration effectively avoids unnecessary shift shock or driving discomfort caused by misjudgment, while ensuring that the vehicle always maintains a stable and efficient operation.

[0012] Through these measures, the present invention not only shortens downshift response time but also improves the smoothness and efficiency of the entire shift process, enhancing vehicle safety and driving experience. Compared to the potential jerking and instability caused by traditional methods, the present invention provides a smoother and safer driving experience.

[0013] In summary, this method can improve the smoothness and response speed of gear shifting, while reducing the wear of mechanical components and enhancing the safety performance and driving experience of the vehicle.

[0014] Preferably, the status data includes the gearbox operating status, throttle opening and throttle change rate.

[0015] Preferably, in S2, when the state data meets the following three requirements at the same time, the prediction result is that power downshift may occur: the transmission operating state is in gear and the gear position is not in 1st gear and R gear, the throttle opening is greater than the preset opening, and the throttle change rate is greater than the preset change rate.

[0016] In this setting, the transmission is in gear and the gear is not in 1st or R: This means the vehicle is moving and the current gear is not the lowest gear or reverse gear. Typically, when accelerating or overtaking, or other maneuvers requiring greater torque, the lowest gear (1st) or reverse gear (R) are not involved, as these gears already offer the maximum gear ratio. The throttle opening is greater than the preset opening: The throttle opening reflects the driver's need for acceleration. When the throttle opening exceeds a preset value, it indicates that the driver desires more power output, perhaps for accelerating overtaking or climbing a hill that requires more torque. The throttle change rate is greater than the preset change rate: The throttle change rate describes the speed at which the accelerator pedal is depressed. A rapid increase in the throttle opening usually indicates an urgent need for acceleration, such as sudden acceleration for overtaking. A high throttle change rate is one of the key indicators for predicting an impending power downshift.

[0017] By comprehensively analyzing these three parameters, it is possible to accurately determine whether a power downshift operation may be necessary and prepare in advance.

[0018] Preferably, in S6, the process of re-engaging the clutch includes: gradually increasing the clutch engagement force according to a preset torque slope, and controlling the engine torque to reduce to the current torque of the clutch.

[0019] This setup 1. Slowly and controlledly increases clutch engagement force, allowing the engine and driveline speeds to gradually synchronize, avoiding the sudden power surges that can occur with a sudden connection. By gradually increasing clutch engagement force rather than abruptly engaging the clutch, a smooth transition in power transmission is ensured, significantly reducing or even eliminating the potential jarring sensation during shifting or re-engaging.

[0020] 2. By precisely controlling the rate of increase in clutch engagement force and the corresponding adjustment of engine torque, continuous and stable power delivery is ensured, avoiding uncomfortable jerks. Because the entire reengagement process is gradual, violent collisions and vibrations between mechanical components are reduced, directly improving vehicle comfort and providing passengers with a smoother and quieter driving experience.

[0021] Preferably, in S1, the vehicle status is obtained at a preset frequency.

[0022] This setup, by setting an appropriate sampling frequency, allows the system to monitor vehicle status changes in real time. This allows the control system to immediately detect changes in driving conditions or vehicle status and respond swiftly. Furthermore, regularly acquiring vehicle status helps enhance the system's ability to respond to unexpected situations. For example, in the event of emergency braking or sudden acceleration, the system can quickly adjust its strategy based on the latest data to ensure driving safety.

[0023] Preferably, the preset frequency is 20 Hz to 100 Hz.

[0024] This setup requires: 1. A vehicle's power downshift typically occurs within a short period of time (e.g., a few hundred milliseconds), necessitating a high sampling frequency to capture changes in key parameters such as throttle opening, throttle change rate, and transmission status. If the sampling frequency is too low (e.g., below 10Hz), the system may not promptly detect driver intent (e.g., rapid accelerator application) or changes in transmission status, thus delaying the power downshift response. A frequency higher than 20Hz ensures that the system can more quickly identify an impending power downshift request.

[0025] 2. While modern automotive electronic control units (ECUs) possess powerful computing capabilities, excessively frequent data collection increases the system's computational load and can lead to data redundancy issues. Frequencies exceeding 100Hz are unnecessary for most automatic transmission applications due to the limited resolution of human perception of the shifting process and the physical limitations of mechanical component response speeds. A frequency range of 20Hz to 100Hz can meet real-time requirements while avoiding excessive computational pressure on the ECU.

[0026] Preferably, in S5 , the downshift control operation includes switching gears after synchronizing the engine speed with the input shaft speed.

[0027] Preferably, the closed-loop control strategy is PID control.

[0028] With this setup, PID control precisely adjusts the difference between engine speed and input shaft speed, keeping it close to the target value. This helps ensure smooth shifting and reduces mechanical shock. Furthermore, PID control offers a fast response time, reacting promptly when the speed difference deviates from the target value while maintaining system stability and avoiding oscillations caused by over-regulation.

[0029] Preferably, the normal driving state is that the clutch is fully engaged and the engine speed is stable.

[0030] With this setup, a fully engaged clutch ensures seamless power transfer between the engine and transmission, while a stable engine speed ensures consistent and smooth output torque. When the clutch is fully engaged and the engine speed is stable, power transmission is optimized, avoiding the jerking and unevenness caused by a partially engaged clutch or fluctuating engine speed. Furthermore, continuous partially engaged clutches can cause overheating and accelerated wear, while unstable engine speeds can put additional stress and shock on internal transmission components. Maintaining a fully engaged clutch and a stable engine speed can help mitigate these issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which: Figure 1 Flowchart of this method. DETAILED DESCRIPTION

[0032] The following is a further detailed description through specific implementation methods: Example: like Figure 1 As shown, this embodiment discloses a clutch pre-disengagement method for power downshifting of a vehicle automatic transmission, comprising the following steps: S1. While the vehicle is traveling, obtain vehicle status data at a preset frequency; wherein the status data includes a transmission operating state, a throttle opening, and a throttle change rate.

[0033] In specific implementation, the preset frequency is 20Hz to 100Hz. By setting an appropriate sampling frequency, the system can monitor vehicle state changes in real time. This allows the control system to immediately detect changes in driving conditions or vehicle status and respond quickly. Furthermore, regularly acquiring vehicle status enhances the system's ability to respond to unexpected situations. For example, in the event of emergency braking or sudden acceleration, the system can quickly adjust its strategy based on the latest data to ensure driving safety. On the one hand, a vehicle's power downshift typically occurs within a short period of time (e.g., within a few hundred milliseconds), necessitating a higher sampling frequency to capture changes in key parameters such as throttle opening, throttle change rate, and transmission status. If the sampling frequency is too low (e.g., below 10Hz), the system may not be able to promptly detect driving intent (e.g., rapid accelerator application) or changes in transmission status, thereby delaying the power downshift response. A frequency above 20Hz ensures that the system can more quickly identify an impending power downshift request. On the other hand, while modern automotive electronic control units (ECUs) possess powerful computing power, overly frequent data collection increases the system's computational load and may lead to data redundancy. Frequencies exceeding 100Hz are unnecessary for most automatic transmission applications due to the limited resolution of human perception of the shifting process and the physical limitations of mechanical component response speeds. A frequency range of 20Hz to 100Hz can meet real-time requirements while avoiding excessive computational pressure on the ECU.

[0034] S2. Predict whether a power downshift will occur based on the acquired status data; if the prediction result is that a power downshift may occur, go to S3; otherwise, return to S1 to re-acquire status data.

[0035] In specific implementation, when the status data meets the following three requirements at the same time, the prediction result is that power downshift may occur: the transmission operating state is in gear and the gear is not in 1st gear and R gear, the throttle opening is greater than the preset opening, and the throttle change rate is greater than the preset change rate.

[0036] The transmission is in gear and the gear is not 1st or R: This means the vehicle is moving and the current gear is not lowest or reverse. Typically, maneuvers requiring greater torque, such as acceleration or overtaking, do not involve lowest (1st) or reverse (R) gear, as these gears already offer the maximum gear ratio. The throttle opening is greater than the preset value: The throttle opening reflects the driver's need for acceleration. When the throttle opening exceeds a preset value, it indicates that the driver desires more power output, perhaps for accelerating overtaking or climbing a hill, which requires more torque. The throttle change rate is greater than the preset value: The throttle change rate describes the speed at which the accelerator pedal is depressed. A rapid increase in throttle opening often indicates an urgent need for acceleration, such as sudden acceleration for overtaking. A high throttle change rate is one of the key indicators for predicting an impending power downshift. By comprehensively analyzing these three parameters, it is possible to accurately determine whether a power downshift is likely to occur and to prepare for it in advance.

[0037] During specific implementation, those skilled in the art may make specific settings according to the type and model of the vehicle, which will not be described in detail here.

[0038] S3. Execute a pre-shift strategy, controlling the clutch to reduce torque according to a preset torque slope, thereby disengaging the clutch. During the clutch disengagement process, a closed-loop control strategy is employed to control the speed difference between the engine and input shaft toward a target speed difference. In practice, the target speed difference can be calculated based on the target downshift position and the current vehicle speed to ensure that, after the downshift is complete, the engine speed quickly matches the new gear, minimizing shift shock. The preset torque slope value can be set by those skilled in the art based on the type and model of the vehicle and is not detailed here.

[0039] The closed-loop control strategy is PID control. PID control precisely adjusts the difference between engine speed and input shaft speed to keep it close to the target value. This helps ensure smooth shifting and reduces mechanical shock. Furthermore, PID control offers a fast response time, enabling it to react quickly when the speed difference deviates from the target value while maintaining system stability and avoiding oscillation caused by over-regulation.

[0040] If a downshift command is received within a preset time period after the pre-shift strategy is started, the process proceeds to S5; if no downshift command is received, the process proceeds to S6. Specifically, the downshift command is automatically generated by the vehicle's automatic gear control system based on the vehicle speed and throttle level.

[0041] S5: End the pre-shift strategy, execute the downshift control operation, and after the downshift control operation is completed and the normal driving state is restored, return to S1. The downshift control operation includes switching the gear after synchronizing the engine and input shaft speeds.

[0042] In specific implementation, the normal driving state is that the clutch is fully engaged and the engine speed is stable. A fully engaged clutch ensures seamless power transmission between the engine and the transmission, while a stable engine speed ensures consistency and smoothness in the output torque. When the clutch is fully engaged and the engine speed is stable, it means that the power transmission has reached the most optimized state, avoiding the sense of frustration and unevenness caused by half-clutch engagement or engine speed fluctuations. In addition, continuous half-engagement can cause clutch overheating and accelerated wear, while unstable engine speed may cause additional stress and impact on the internal components of the transmission. Keeping the clutch fully engaged and the engine speed stable can help alleviate these problems.

[0043] S6: Reengage the clutch, and return to S1 after normal driving resumes. The clutch reengagement process involves gradually increasing clutch force according to a preset torque ramp while simultaneously reducing engine torque to the clutch's current torque level. This slow and controlled increase in clutch force allows for gradual synchronization of engine and driveline speeds, avoiding sudden power surges caused by a sudden connection. By gradually increasing clutch force, rather than abruptly engaging the clutch, a smooth transition in power transmission is ensured, significantly reducing or even eliminating the potential jerkiness associated with shifting or reengaging. Furthermore, by precisely controlling the rate of increase in clutch force and the corresponding engine torque adjustment, continuous and stable power transmission is ensured, avoiding uncomfortable jerks. Because the reengagement process is gradual, significant impact and vibration between mechanical components are reduced, directly improving vehicle comfort and providing a smoother, quieter ride for passengers.

[0044] This method acquires real-time vehicle status data (such as transmission status, throttle opening, and rate of change) during vehicle maneuvers. Based on this data, it predicts whether a power downshift will occur and executes the corresponding action based on the prediction. Compared to existing methods that rely on fixed shift points, this method more accurately identifies driver intent and enables proactive response. Traditional methods often only initiate downshifts when a downshift is actually required, while the present invention enables immediate preparation when an impending downshift is predicted, significantly improving response speed and accuracy. When a power downshift is predicted, the present method implements a pre-shift strategy to increase engine speed in advance and pre-disengage the clutch before issuing a power downshift command, saving time for the subsequent power downshift. This process not only speeds up downshifts but also avoids engine roar caused by sudden acceleration, improving ride comfort. Compared to the delay and potential noise associated with direct downshifts, the present invention ensures a smoother and quieter downshift by pre-adjusting engine speed, thereby ensuring a smoother and quieter downshift.

[0045] Furthermore, a closed-loop control strategy manages the clutch disengagement and engagement processes, ensuring the speed differential between the engine and input shaft remains within the target range. This closed-loop control system dynamically adjusts engine torque or clutch engagement force based on the measured speed differential, precisely controlling power delivery and avoiding mechanical shock caused by speed mismatch. The closed-loop control strategy monitors and adjusts the speed differential between the engine and input shaft in real time, keeping them as close to the preset target speed differential as possible. This significantly reduces shift shock, resulting in smoother shifts and improved driving comfort. Furthermore, closed-loop control continuously corrects errors through a continuous feedback mechanism, ensuring the speed differential between the engine and input shaft always approaches the ideal value, improving overall system responsiveness. Compared to open-loop control, closed-loop control can more quickly respond to changes and make appropriate adjustments. This means that when a power downshift is detected, the system can react quickly, ensuring fast and accurate shifts. Furthermore, if a downshift command is received within a preset time after the pre-shift strategy begins, the downshift control operation will be executed. If no downshift command is received (i.e., no power downshift occurs subsequently), the method will re-engage the clutch and resume normal driving. This configuration effectively avoids unnecessary shift shock or driving discomfort caused by misjudgment, while ensuring that the vehicle maintains a stable and efficient operation.

[0046] Through the aforementioned measures, the present invention not only shortens downshift response time but also improves the smoothness and efficiency of the entire shifting process, enhancing vehicle safety and the driving experience. Compared to the potential jerkiness and instability associated with traditional methods, the present invention provides a smoother and safer driving experience. In summary, this method improves shifting smoothness and responsiveness while reducing wear on mechanical components, enhancing vehicle safety and the driving experience.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A clutch pre-disengagement method for power downshifting of a vehicle automatic transmission, characterized in that: The following steps are involved: S1. Acquire vehicle status data while the vehicle is traveling; S2. Predict whether a power downshift will occur based on the acquired status data; if the prediction result is that a power downshift may occur, proceed to S3; otherwise, return to S1 to reacquire status data; S3: Execute the pre-disengagement strategy to control the clutch to reduce torque according to the preset torque slope and disengage the clutch; A closed-loop control strategy is used during the clutch disengagement process to control the speed difference between the engine and the input shaft to change toward the target speed difference; S4: If a downshift command is received within a preset time after the pre-shift strategy is started, go to S5; if not, go to S6; S5, ending the pre-shift strategy, executing the downshift control operation, and returning to S1 after the downshift control operation is completed and the normal driving state is restored; S6. Reengage the clutch and return to S1 after returning to normal driving state.

2. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, characterized in that: The status data includes the transmission operating status, throttle opening and throttle change rate.

3. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 2, characterized in that: In S2, when the status data meets the following three requirements at the same time, the prediction result is that power downshift may occur: the transmission operating state is in gear and the gear is not in 1st gear or R gear, the throttle opening is greater than the preset opening, and the throttle change rate is greater than the preset change rate.

4. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, wherein: In S6, the process of re-engaging the clutch includes gradually increasing the clutch engagement force according to a preset torque slope, while controlling the engine torque to reduce to the current torque of the clutch.

5. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, characterized in that: In S1, the vehicle status is obtained according to a preset frequency.

6. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 5, characterized in that: The preset frequency is 20Hz ~ 100Hz.

7. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, wherein: In S5, the downshift control operation includes switching gears after synchronizing the engine and input shaft speeds.

8. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, wherein: The closed-loop control strategy is PID control.

9. The clutch pre-disengagement method for power downshifting of an automatic transmission of a vehicle according to claim 1, characterized in that: The normal driving state is that the clutch is fully engaged and the engine speed is stable.

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