Hydraulic Clutch Pre-staging for Hybrid Regenerative Braking
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Solution Overview
Problem
Regenerative braking efficiency in hybrid vehicles is reduced at lower speeds due to the time required for downshifting the transmission, which limits the time available for electricity generation.
Innovation Solution
A controller boosts and strokes the hydraulic cylinder of an on-coming clutch before the disconnect clutch is opened, allowing for a pre-staged downshift that reduces the delay in shifting gears, enabling direct shifts and optimizing hydraulic pressure to enhance regenerative braking efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmission is downshifted to increase e-machine speed and regenerative braking efficiency, then the available torque and efficiency are improved, but the time required for downshifting reduces the time available for regenerative braking
Solution Approach 1:
The hydraulic cylinder of the on-coming clutch is boosted and stroked in advance before the disconnect clutch is opened and the downshift is executed. This pre-staging of the clutch actuator reduces the actual shift execution time, allowing more time for regenerative braking while maintaining the ability to perform the downshift when needed.
2Loss of time
If the hydraulic cylinder is boosted and stroked before downshifting, then the downshift time is reduced, but the complexity of the control system increases
Solution Approach 1:
The control system dynamically adjusts the hydraulic pressure to the clutch actuator based on real-time conditions. The controller monitors battery state-of-charge, vehicle speed, and driver input to determine when to pre-boost and stroke the hydraulic cylinder, optimizing the balance between shift speed and control complexity.
Solution Approach 2:
The controller uses feedback from various sensors (battery state-of-charge, vehicle speed, pedal position) to intelligently control when to pre-charge and stroke the hydraulic cylinder. This feedback mechanism allows the system to adapt to different driving conditions and only activate the pre-staging function when it will benefit regenerative braking.
3Power
If regenerative braking is maintained at high levels during downshift, then electricity generation is maximized, but shift quality deteriorates
Solution Approach 1:
The hydraulic cylinder is pre-charged and stroked before the downshift begins, so that the clutch is already prepared for engagement. This preliminary preparation allows the shift to be executed quickly with minimal reduction in regenerative braking, as the clutch components are already in position and the hydraulic pressure is pre-established.
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
This approach increases the time available for regenerative braking, allowing more kinetic energy to be recaptured and improving fuel economy by reducing the downshift time and maintaining acceptable shift quality.
Implementation Method 1
a plurality of clutches that are each engaged and disengaged by a hydraulic cylinder
Implementation Method 2
Kinetic energy of the vehicle is converted to electricity used to charge a high voltage battery using an e-machine as a brake and a generator
Data Source
AI summary
A hybrid vehicle has a battery, a regenerative braking system, a transmission, and a controller. The controller boosts and strokes a hydraulic cylinder of an on-coming clutch when the state-of-charge of the battery allows regenerative braking and in response to a pedal actuation. The controller boosts and strokes the hydraulic cylinder before a disconnect clutch is opened and the transmission is downshifted to increase regenerative braking efficiency.