DCT Shift Control Torque Handover Tip-Out Compensation
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Solution Overview
Problem
Dual Clutch Transmissions (DCTs) experience shock and vibration when a driver suddenly releases the accelerator pedal during power-on up-shifting to an upper gear, due to rapid engine torque decrease, as they lack a mechanism to absorb shifting shocks like torque converters in automatic transmissions.
Innovation Solution
A shift control method that involves a controller to perform torque handover control by calculating and adjusting the control torques of the release-side and engage-side clutches, determining tip-out conditions, and recalculating the remaining torque handover period to apply different control torques and prevent shock, using a map-based approach to account for engine torque changes and engine revolutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power-on up-shifting is performed with accelerator pedal pressed down, then shifting speed is improved, but shock and vibration occur due to sudden engine torque changes when driver releases accelerator
Solution Approach 1:
The controller predicts future engine torque changes based on current accelerator pedal position and opening degree changes. By anticipating the torque drop that will occur when the driver releases the accelerator, the system prepares the clutch torque handover in advance, ensuring smooth transition despite the upcoming torque change. This predictive approach allows maintaining fast shifting speed while preventing shock and vibration.
Solution Approach 2:
The system continuously monitors accelerator pedal opening degree changes and uses this feedback to adjust clutch control torques dynamically. When rapid opening degree change is detected (indicating driver is releasing accelerator), the controller modifies the torque handover profile to compensate for the impending torque drop, thereby preventing shock and vibration during the shifting process.
2Loss of energy
If DCT uses synchro-mesh type shifting mechanism without torque converter, then mechanical efficiency is improved, but shock and vibration occur due to lack of shock absorption mechanism
Solution Approach 1:
The patent replaces the mechanical shock absorption function of a torque converter with an electronic control system that actively manages clutch torque handover. The controller calculates optimal clutch control torques based on engine torque characteristics and shifting phase, substituting the passive mechanical damping of a torque converter with active electronic torque management. This maintains the mechanical efficiency of the synchro-mesh DCT while eliminating shock and vibration through precise torque control.
3Loss of time
If clutch torque handover is performed rapidly, then shifting time is reduced, but precision of torque control deteriorates causing shock and vibration
Solution Approach 1:
The controller dynamically adjusts the torque handover profile based on the detected shifting phase and predicted engine torque changes. During normal conditions, torque handover is performed rapidly for efficient shifting. When accelerator release is predicted, the system dynamically modifies the torque transfer curve to ensure smooth transition, optimizing the balance between shifting speed and torque control precision in real-time.
Solution Approach 2:
The system changes the control parameters (clutch control torques) based on the detected accelerator pedal opening degree变化 rate and predicted engine torque characteristics. By adjusting torque handover parameters dynamically according to driving conditions, the system achieves both fast shifting and precise torque control, preventing shock and vibration even during rapid accelerator release.
Data Source
AI summary
A shift control method for a vehicle with a Dual Clutch Transmission (DCT) may include determining whether power-on up-shifting has been initiated, performing torque handover control by controlling release-side and engage-side clutches by repeatedly calculating control torques of the release-side clutch and the engage-side clutch over time, when the power-on up-shifting is started and a torque handover period is entered, determining whether tip-out is generated during the performing of torque handover control, obtaining a remaining updating time by recalculating a remaining time until the end of the torque handover period in accordance with a decrease in engine torque, when it is determined that tip-out has been generated, and controlling the release-side and the engage-side clutches on the basis of the control torques for the release-side and the engage-side clutches that are made different in accordance with the calculated remaining updating time during a remaining torque handover period.