Expansion Combustion Engine Start Fuel Control
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Solution Overview
Problem
Frequent engine restarts in start-stop systems lead to increased wear on the starter motor due to unpredictable torque production from expansion combustion, caused by varying air mass in the cylinder during auto-stop conditions, resulting in misfires and inefficient air-fuel ratio control.
Innovation Solution
A method to determine the fuel mass for restart combustion based on the duration of auto-stop, accounting for aircharge variations by modeling the initial and equilibrium aircharges, and adjusting for pressure changes over time, ensuring accurate air-fuel ratio control and robust engine restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If expansion combustion is used to reduce starter motor wear, then starter motor wear is reduced, but air-fuel ratio control deteriorates due to varying air mass in the cylinder during auto-stop
Solution Approach 1:
The controller performs preliminary actions by tracking air mass variations throughout the auto-stop period and pre-calculating the required fuel injection amount before combustion. This allows the system to compensate for air leakage effects in advance, ensuring accurate air-fuel ratio control while maintaining the benefits of expansion combustion for reducing starter motor wear.
Solution Approach 2:
The system implements feedback by continuously monitoring cylinder pressure and temperature during the auto-stop period, using this information to dynamically adjust fuel injection timing and quantity. This closed-loop control compensates for air mass changes, maintaining precise air-fuel ratio control despite the expanding combustion chamber volume during engine shutdown.
2Loss of time
If expansion combustion is used to assist engine restart, then engine restart time is reduced, but combustion reliability deteriorates due to misfire from unaccounted air mass changes
Solution Approach 1:
The controller performs preliminary tracking of air mass variations from the moment the engine shuts down, using this data to pre-determine the optimal fuel injection quantity before combustion occurs. This preliminary calculation ensures that the air-fuel mixture is correctly proportioned, preventing misfire and ensuring reliable combustion while enabling quick engine restart.
Solution Approach 2:
The system dynamically changes combustion parameters (fuel injection timing, quantity, and rate) based on real-time measurements of cylinder pressure and temperature. By adjusting these parameters according to the actual air mass present in the cylinder, the system maintains combustion reliability across varying auto-stop durations while achieving rapid engine restart.
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 enhances the reliability and robustness of engine restarts, reduces starter motor wear, and decreases engine restart times, thereby improving customer satisfaction and fuel efficiency.
Implementation Method 1
actuating a spark plug of the cylinder to perform the restart combustion event
Data Source
AI summary
Methods and systems are provided for performing expansion combustion in an engine of a start-stop vehicle. In one example, a method may include, responsive to receiving an auto-start request to restart an engine from an auto-stop, determining a fuel mass to inject into a cylinder for an expansion combustion event based on a duration of the auto-stop, and actuating a spark plug of the cylinder after injecting the determined fuel mass to perform the expansion combustion event. In this way, an air-fuel ratio of the expansion combustion event may be more accurately controlled, resulting in more robust expansion combustion engine restarts.