Starter-Generator Drag Torque for Engine Start Overshoot
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Solution Overview
Problem
In hybrid vehicles, it is challenging to prevent engine speed overshoot during engine starts, especially when the target speed is low, as increasing spark retard alone may not be sufficient, leading to inefficiencies in fuel consumption and emissions.
Innovation Solution
A controller is programmed to generate a target drag torque with the starter-generator during engine start-up events to adjust engine speed, reducing overshoot by increasing the engine load, thereby minimizing the need for excessive spark retard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If spark retard is increased to reduce engine torque during engine starts, then engine speed overshoot is reduced, but fuel consumption increases and emissions worsen
Solution Approach 1:
The starter-generator acts as an intermediary device to apply drag torque to the engine during start-up, providing a controlled opposing force that stabilizes engine speed without requiring excessive spark retard, thereby reducing fuel consumption and emissions
Solution Approach 2:
The system dynamically changes the load parameter by controlling the starter-generator torque output, adjusting the drag torque applied to the engine based on real-time engine speed feedback to optimize both speed stability and fuel efficiency
2Stability of the object's composition
If starter-generator drag torque is applied to reduce engine speed overshoot, then engine speed control is improved, but device complexity increases
Solution Approach 1:
The starter-generator is designed to perform multiple functions: it serves as both a starting motor and a drag torque application device for engine speed control during start-up, eliminating the need for separate control mechanisms and reducing overall system complexity
Solution Approach 2:
The control system uses feedback from engine speed sensors to dynamically adjust the starter-generator torque output, creating a closed-loop control system that automatically maintains engine speed within target ranges without requiring complex manual intervention
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 effectively reduces engine speed overshoot, improves fuel economy, and decreases emissions by allowing for earlier closure of the disconnect clutch, enhancing overall engine start efficiency.
Implementation Method 1
The starter-generator is coupled to the engine and is configured to adjust engine speed during an engine start-up event
Data Source
AI summary
A vehicle includes an engine, electric machine, starter-generator, and a controller. The engine and electric machine are each configured to propel the vehicle. The starter-generator is coupled to the engine and is configured to adjust engine speed during an engine start-up event. The controller is programmed to, in response to engine speed increasing towards a target speed during an engine start-up event, generate a target drag torque with the starter-generator to reduce overshoot of the target engine speed.