Hybrid Electric Machine Torque Control During Engine Start
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In hybrid vehicles, when starting the engine by closing a driveline disconnect clutch, there is often insufficient torque capacity to avoid reducing driveline speed, leading to suboptimal vehicle performance.
Innovation Solution
Estimating the maximum motor propulsive torque based on a predicted torque converter impeller speed at the end of the engine cranking period, and limiting driver demand torque to this maximum during engine starting to ensure sufficient torque for both engine cranking and vehicle propulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric machine provides maximum propulsive torque during engine cranking, then vehicle propulsion performance is improved, but engine starting reliability deteriorates due to insufficient torque capacity
Solution Approach 1:
The patent dynamically adjusts the propulsive torque generated by the electric machine during engine cranking based on real-time driveline speed feedback. The controller continuously monitors driveline speed and modulates the electric machine torque output to maintain driveline speed above a threshold, transitioning from static maximum torque provision to dynamic adaptive torque control that balances propulsion needs with engine starting requirements
Solution Approach 2:
The patent predicts the torque converter impeller speed at the end of the engine cranking period before cranking actually completes. This preliminary prediction allows the system to pre-determine the maximum propulsive torque capacity in advance, enabling proactive torque management that ensures sufficient torque is reserved for engine starting while maintaining optimal vehicle propulsion performance throughout the cranking process
2Reliability
If the electric machine reserves sufficient torque for engine starting, then engine starting reliability is improved, but vehicle propulsion performance deteriorates
Solution Approach 1:
Rather than statically reserving a fixed portion of electric machine torque for engine starting, the system dynamically allocates torque between propulsion and starting functions. The controller continuously adjusts the propulsive torque based on driveline speed measurements, allowing maximum propulsion when driveline speed is adequate and automatic torque reservation when driveline speed approaches the threshold, optimizing both propulsion performance and starting reliability
3Reliability
If the driveline disconnect clutch is closed to start the engine, then engine starting is achieved, but driveline torque disturbances occur due to insufficient torque capacity
Solution Approach 1:
The patent implements a closed-loop feedback control system where the controller continuously monitors driveline speed during engine cranking and adjusts the electric machine torque output accordingly. When driveline speed approaches the threshold, the controller reduces propulsive torque to prevent further speed reduction, thereby maintaining driveline torque stability and preventing torque disturbances while ensuring successful engine starting
Solution Approach 2:
The system performs preliminary prediction of the torque converter impeller speed at cranking completion to anticipate future torque requirements. This allows the controller to pre-adjust the propulsive torque profile during cranking to ensure that sufficient torque capacity will be available at the critical moment when the clutch closes and engine starting begins, preventing torque disturbances before they occur
Data Source
AI summary
Systems and methods for starting an engine that may be started via an electric machine and a driveline disconnect clutch are described. In one example, the method estimates a maximum motor propulsive torque during engine starting. The maximum motor propulsive torque may be based on an estimated speed that a torque converter impeller speed will be when an engine cranking period ends.