DCT Upshift Control for Flare Reduction
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Solution Overview
Problem
During power-on upshifting in vehicles equipped with dual clutch transmissions (DCTs), the flare phenomenon occurs due to mismatched increases in engine torque and engaging clutch torque, leading to unsynchronized engine speed with the target shift-stage input shaft speed, resulting in shifting shocks.
Innovation Solution
An upshift control method that determines and calculates specific clutch torque adjustments based on accelerator pedal depression differences and slip change rates to synchronize engine speed with the target shift-stage input shaft speed, preventing excessive clutch torque increases and ensuring smooth shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engaging clutch torque is increased in response to an increase in engine torque during power-on upshifting, then the flare phenomenon is prevented, but excessive change to engine angular acceleration occurs causing shocks at the end of shifting
Solution Approach 1:
The patent applies dynamics by making the clutch torque control adaptive and variable throughout the shifting process. The controller dynamically adjusts the engaging clutch torque based on the current shifting phase (torque phase or inertia phase) and the rate of change of accelerator pedal depression amount. This dynamic control strategy prevents the flare phenomenon during the torque phase while avoiding excessive engine angular acceleration changes during the inertia phase, thereby eliminating shocks at the end of shifting.
Solution Approach 2:
The patent changes the control parameters based on the shifting phase and accelerator pedal depression rate. During the torque phase, the engaging clutch torque is increased to match engine torque increase and prevent flare. During the inertia phase, when accelerator pedal depression rate exceeds a threshold, the torque increase is limited to prevent excessive engine angular acceleration. This parameter-based control resolves the contradiction between preventing flare and avoiding shocks.
2Speed
If the engine torque increases in response to accelerator pedal depression during power-on upshifting, then the vehicle acceleration performance is improved, but the engaging clutch torque does not increase at the same rate causing flare phenomenon
Solution Approach 1:
The patent employs feedback control by continuously monitoring the accelerator pedal depression amount and its rate of change, and adjusting the engaging clutch torque accordingly. The controller receives feedback on the current shifting phase and accelerator pedal operation, then modulates the clutch torque to maintain synchronization between engine speed and target input shaft speed while enabling vehicle acceleration.
Solution Approach 2:
The patent applies preliminary action by pre-defining control strategies for different shifting phases (torque phase and inertia phase). Before the shifting completes, the controller anticipates the need to adjust clutch torque based on the detected phase and accelerator pedal rate, preventing flare phenomenon before it occurs rather than correcting it after.
Data Source
AI summary
An upshift control method for a dual clutch transmission (DCT) for a vehicle includes: determining, by a controller, whether or not an inertia phase begins when a driver accelerator pedal depression amount increases during power-on upshifting; calculating, by the controller, a first control amount, which is a first final clutch torque for controlling an engaging clutch, when the inner phase begins, in consideration of a difference between a current accelerator pedal depression amount and an accelerator pedal depression amount at beginning of the inertia phase, a difference between the current accelerator pedal depression amount and a maximum value of an accelerator pedal depression amount during the inertia phase elapsed until a present time, and a target engine torque, and controlling, by the controller, the engaging clutch with the final clutch torque calculated in the calculating.