Hybrid DCT Shift Control for Smooth Power-Off Downshift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid vehicles with Double Clutch Transmission (DCT) face challenges in performing smooth power-off down-shift during heavy braking, as existing methods do not effectively manage regenerative braking torque and clutch torque, leading to inefficient shifting quality.
Innovation Solution
A shift control method that determines the inertia phase of power-off down-shift and adjusts regenerative braking torque and engagement clutch torque based on predetermined reduction amounts, calculated using equations involving clutch torque, slip change rate, and speed change rate, to facilitate quick and smooth shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking torque is maintained during power-off down-shift, then energy recovery is improved, but shifting smoothness deteriorates
Solution Approach 1:
The patent dynamically adjusts regenerative braking torque based on the shifting phase. During the inertia phase of power-off down-shift, the controller reduces regenerative braking torque to prevent torque conflicts that would cause shifting shock. This dynamic adjustment allows the system to optimize both energy recovery and shifting smoothness by adapting torque levels to the current shifting state.
Solution Approach 2:
The controller detects the entry into the inertia phase and proactively reduces regenerative braking torque before the shifting conflict occurs. By anticipating the torque demand changes during down-shift, the system prepares the motor torque in advance, preventing shifting shock and ensuring smooth gear transition while maintaining optimal energy recovery.
2Ease of operation
If regenerative braking torque is reduced during inertia phase, then shifting smoothness is improved, but energy recovery efficiency deteriorates
Solution Approach 1:
The system dynamically modulates regenerative braking torque based on real-time shifting phase detection. During the inertia phase, torque is reduced to ensure smooth shifting, while during other phases, full regenerative braking is maintained for optimal energy recovery. This dynamic control strategy resolves the contradiction by optimizing torque levels for each specific operating condition.
Solution Approach 2:
The controller changes the regenerative braking torque parameter according to the shifting phase. By detecting the inertia phase entry and adjusting the torque parameter accordingly, the system achieves both smooth shifting and efficient energy recovery. The parameter change is temporary and reversible, allowing the system to maintain optimal performance across different operating conditions.
3Speed
If clutch torque is not reduced during inertia phase, then shifting speed is improved, but shifting shock increases
Solution Approach 1:
The controller continuously monitors clutch torque and motor speed during the shifting process. Based on feedback from speed sensors and torque sensors, the system adjusts clutch torque reduction timing and magnitude to achieve smooth shifting without compromising shifting speed. The feedback mechanism allows real-time optimization of the torque transition profile.
Solution Approach 2:
The controller proactively reduces clutch torque upon detecting the inertia phase entry, preparing the clutch for smooth engagement before the actual gear switch occurs. This preliminary torque reduction prevents torque conflicts and shifting shock, while the controlled reduction rate maintains acceptable shifting speed by avoiding abrupt torque changes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method improves shifting quality by rapidly reducing regenerative braking torque during the inertia phase and synchronizing motor and input shaft speeds, preventing shifting shock and enhancing commercial value by ensuring smooth power-off down-shift in heavy braking conditions.
Implementation Method 1
In a hybrid vehicle, regenerative braking using a motor is performed to increase fuel efficiency while a vehicle is decelerated, and the power generated in this process is returned as electric energy.
Implementation Method 2
a clutch torque-reducing step that ends the motor torque-adjusting step and reduces torque of an engagement clutch
Implementation Method 3
a shifting state-determining step in which a controller determines whether an inertia phase of power-off down-shift has been entered
Data Source
AI summary
The present disclosure provides a shift control method for a hybrid vehicle with a DCT that includes: a shifting state-determining step in which a controller determines whether an inertia phase of power-off down-shift is entered; a motor torque-adjusting step that request to reduce regenerative braking torque of a motor as much as a predetermined requested reduction amount, when the controller determines that the inertia phase has been entered in the shifting state-determining step; and a clutch torque-reducing step that ends the motor torque-adjusting step and reduces torque of an engagement clutch, when the requested reduction amount of the regenerative braking torque of the motor is less than zero while the controller performs the motor torque-adjusting step.