DCT Shifting Control for Same-Shaft Downshifts
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Solution Overview
Problem
Dual-clutch transmissions (DCTs) face lower responsiveness during same-shaft power on down shifts due to their hardware structure, which requires sequential different-shaft shifting, resulting in slower shifting compared to conventional automatic transmissions.
Innovation Solution
A shifting control method that involves controlling the torque of clutches in a DCT to minimize torque interruption by preparing and handover steps, including adjusting clutch torques and gear engagements to synchronize engine rotation speed with target clutch speeds, allowing for faster and smoother same-shaft power on down shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If same-shaft shifting is performed by sequentially performing different-shaft shifting in DCT, then the hardware structure constraint is satisfied, but the shifting responsiveness deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-engaging the target gear before disengaging the current gear. Specifically, the gear for the target shifting stage is engaged in advance while the clutch is still connected to the current shifting stage, allowing the gear to be ready before torque transfer begins. This preliminary gear engagement significantly reduces shifting time and improves responsiveness during same-shaft shifting operations.
2Reliability
If torque is transferred sequentially through multiple clutches during same-shaft shifting, then torque interruption is minimized, but shifting time increases
Solution Approach 1:
The patent merges the gear engagement action with the clutch torque transfer action into a single coordinated operation. By engaging the target gear while the clutch is still connected to the current shifting stage, and then transferring torque to the target clutch simultaneously, the patent combines what would otherwise be sequential operations into a merged process that maintains torque continuity while reducing shifting time.
3Duration of action of moving object
If DCT uses separate clutches for odd and even shifting stages, then clutch wear is reduced, but same-shaft shifting responsiveness deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-engaging the target gear before disengaging the current gear. Specifically, the gear for the target shifting stage is engaged in advance while the clutch is still connected to the current shifting stage, allowing the gear to be ready before torque transfer begins. This preliminary gear engagement significantly reduces shifting time and improves responsiveness during same-shaft shifting operations.
Data Source
AI summary
A shift control method of a vehicle with a dual clutch transmission (DCT) may include: a first preparing step of, by a controller, controlling a torque of an N-th stage clutch to a predetermined minimum torque and increasing a torque of an N−1-th stage clutch to a predetermined standby torque; a first handover step of releasing the torque of the N-th stage clutch and increasing the torque of the N−1-th stage clutch; a gear changing step of releasing an N-th stage gear and then initiating an engagement of an N−2-th stage gear; a synchronization maintaining step of maintaining a synchronized state by adjusting the torque of the N−1-th stage clutch; a second preparing step of increasing the torque of the N−2-th stage clutch to the standby torque; and a second handover step of releasing the torque of the N−1-th clutch and increasing the torque of the N−2-th stage clutch.