HEV Shift Coordination With Engine Torque Fill During EV Gear Changes
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Solution Overview
Problem
Conventional hybrid-electric vehicle (HEV) powertrain systems experience a 'dead pedal' issue during electric motor gear shifts, where the vehicle feels unresponsive due to a lack of torque delivery despite driver input, as the electric motor is disconnected and synchronized with the target gear.
Innovation Solution
A hybrid powertrain control system that coordinates electric motor gear shifts and engine starts by monitoring transmission gear shifts, detecting driver torque requests, and activating the internal combustion engine to provide torque during gear shifts, using a synchronization ratio to determine the optimal timing for engine engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is disconnected from the geartrain to perform gear shift synchronization, then the gear change can be completed successfully, but torque delivery to the wheels is interrupted causing a dead pedal effect
Solution Approach 1:
The internal combustion engine acts as an intermediary torque source during the gear shift transition. When the electric motor is disconnected for synchronization, the engine provides torque through the transmission to maintain continuous torque delivery to the wheels, eliminating the dead pedal effect while allowing the gear shift to complete successfully
Solution Approach 2:
The controller predicts the gear shift timing based on electric motor speed and transmission state, and proactively activates the engine before the electric motor disconnects. This preliminary engine activation ensures torque is already available when the electric motor is disconnected, preventing torque interruption and improving driver experience
2Ease of operation
If the engine is activated during every gear shift, then continuous torque delivery is ensured, but unnecessary engine starts increase energy consumption and mechanical wear
Solution Approach 1:
The controller continuously monitors the gear shift progression by calculating the synchronization ratio based on electric motor speed, target gear speed, and transmission state. This feedback allows the system to determine the optimal timing for engine activation and deactivation, ensuring the engine runs only when necessary to provide torque during the shift, thereby minimizing energy consumption while maintaining torque continuity
Solution Approach 2:
Instead of keeping the engine running throughout the entire gear shift process, the system applies partial action by activating the engine only for the specific duration and conditions when torque support is needed (when synchronization ratio indicates electric motor is disconnected or about to disconnect). This reduces unnecessary engine operation and associated energy losses
3Loss of time
If the engine start is delayed until gear shift begins, then engine activation timing is optimized, but torque interruption occurs during the synchronization phase
Solution Approach 1:
The controller calculates the predicted gear shift timing based on current electric motor speed, target gear speed, and transmission synchronization requirements. Using this prediction, the engine is activated in advance before the electric motor disconnects, ensuring torque is already available from the engine when the electric motor is disconnected, thus preventing any torque interruption while optimizing the overall timing
Data Source
AI summary
A hybrid electric vehicle (HEV) includes an internal combustion engine, an electric traction motor, a motor/generator configured to start the internal combustion engine, a transmission, and a powertrain control system including a controller having one or more processors. The controller is programmed to monitor the transmission for a gear shift while the HEV operates in an EV mode where the electric traction motor provides propulsion for the HEV, detect a driver torque request during the gear shift, and turn the internal combustion engine on to provide torque to the HEV during the gear shift.