Hybrid Engine Torque Modulation for Clutch Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hybrid electric vehicle powertrains, existing systems face challenges in synchronizing engine and motor speeds during tip-in events to efficiently engage the disconnect clutch, leading to suboptimal torque transfer and propulsion.
Innovation Solution
A controller and control strategy that modulates engine torque to rapidly increase engine speed to match motor speed before engaging the disconnect clutch, ensuring smooth transition from disengaged to engaged state, allowing engine torque to be effectively transferred to the transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the disconnect clutch is engaged while engine speed is much lower than motor speed, then the engine can provide torque to the transmission, but the speed difference causes poor torque transfer and potential driveline disturbance
Solution Approach 1:
The control system performs preliminary speed synchronization by modulating engine torque before clutch engagement. The engine torque is initially increased rapidly to raise engine speed toward motor speed, then cut to a reduced level to slow the rate of speed increase, achieving synchronization before the disconnect clutch is engaged. This preliminary action ensures the engine and motor speeds are matched, preventing driveline disturbance during torque transfer.
2Speed
If engine torque is increased rapidly to synchronize engine speed with motor speed, then clutch engagement can be achieved, but the rapid torque change may cause transient disturbances
Solution Approach 1:
The control system applies periodic modulation to engine torque during the synchronization process. Engine torque is initially increased rapidly, then cut to a reduced level, and subsequently increased again after synchronization is achieved. This periodic action pattern allows the engine speed to track motor speed while managing the rate of change, reducing transient disturbances compared to continuous rapid torque application.
3Loss of energy
If the disconnect clutch remains disengaged during coasting, then the engine is disconnected from the transmission, but the engine speed becomes much lower than motor speed requiring synchronization before engagement
Solution Approach 1:
The control system continuously monitors both engine speed and motor speed, calculating the speed difference between them. Based on this feedback, the controller modulates engine torque to reduce the speed difference. The feedback loop adjusts engine torque dynamically - increasing it when the speed difference is large and reducing it when speeds are close - thereby achieving synchronization while maintaining coasting efficiency.
Data Source
AI summary
A system and method for controlling a hybrid vehicle having an engine, a traction motor, and a transmission selectively coupled in series by a clutch include modulating engine torque while the clutch is disengaged and while engine speed is less than motor speed to increase the engine speed. The clutch is engaged to connect the engine to the motor in response to the engine speed exceeding the motor speed.