Hybrid Vehicle Engine Start via Predicted Torque Converter Impeller Speed
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Solution Overview
Problem
Hybrid electric vehicles face challenges in efficiently managing power demands, particularly when the traction motor cannot provide sufficient power or the battery state of charge is low, leading to engine activation issues.
Innovation Solution
A method is implemented where a controller outputs an engine speed command based on predicted impeller speed from a torque converter model, engaging the disconnect clutch when the motor/generator torque limits are reached, to ensure seamless power delivery and prevent engine saturation during increased accelerator pedal tip-ins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is shut down when power demands are low, then fuel economy is improved, but the engine cannot provide power when the traction motor cannot meet the demand
Solution Approach 1:
The controller predicts the impeller speed based on the torque converter model and accelerator tip-in detection before the engine actually needs to start. By calculating the required engine speed command in advance based on predicted impeller speed, the system prepares the engine for immediate startup, ensuring power availability while maintaining fuel economy during low-demand periods.
2Power
If the engine is activated to supplement power output, then power availability is improved, but fuel consumption increases
Solution Approach 1:
The engine speed command is dynamically adjusted based on the predicted impeller speed from the torque converter model. Rather than activating the engine at a fixed speed, the system continuously adapts the engine speed command to match the actual operating conditions and torque converter state, optimizing the balance between power output and fuel consumption.
Solution Approach 2:
The controller uses feedback from the torque converter model and accelerator tip-in detection to continuously adjust the engine speed command. The system monitors the predicted impeller speed and modifies the engine operation accordingly, ensuring the engine provides necessary power while minimizing fuel consumption through precise control.
3Reliability
If the disconnect clutch is engaged when M/G torque limits are reached, then power delivery continuity is improved, but the system complexity increases
Solution Approach 1:
The controller predicts the impeller speed and determines the appropriate engine speed command before the M/G actually reaches its torque limits. By anticipating the need for engine engagement based on the torque converter model, the system prepares the disconnect clutch for engagement, ensuring smooth power delivery continuity without requiring complex real-time decision-making at the moment of limit reach.
Data Source
AI summary
A method for operating a powertrain of a hybrid vehicle is provided. The method includes outputting via a controller an engine speed command that is based on a predicted impeller speed of a torque converter and corresponds to the accelerator tip-in to output a torque from the engine to wheels of the vehicle in response to detection of an accelerator pedal tip-in greater than a predetermined threshold. The method may also include accessing a history of impeller speed outputs of the hybrid vehicle to obtain the predicted impeller speed. The engine speed command may set engine speed substantially equal to or greater than the predicted impeller speed. The predetermined threshold may be based on a driver requested torque output of the wheels in which torque from the torque converter to the wheels results in saturation.