Vehicular Engine Control Device for Lean Combustion Mode
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Solution Overview
Problem
Internal combustion engines face challenges in maintaining a lean combustion mode under varying engine conditions, leading to increased NOx emissions due to insufficient air supply when the battery is undercharged, which affects the operation of electric intake air supply devices and the functionality of three-way catalysts.
Innovation Solution
A control method and device that predefine stoichiometric and lean combustion operation regions based on engine torque and speed, determining the required electric energy for the electric intake air supply device and continuing stoichiometric combustion mode when the battery is insufficiently charged to prevent NOx emissions and ensure effective exhaust gas purification by a three-way catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an electric intake air supply device is employed to achieve lean combustion mode, then fuel consumption is reduced, but when the battery is in an insufficient state of charge, the motor rotation speed falls and air supply becomes short, causing the actual air fuel ratio to become lower than the target lean air fuel ratio and increasing engine-out NOx emission quantity
Solution Approach 1:
The control device acts as an intermediary between the battery state and combustion mode selection. It monitors battery charge state and intervenes in the combustion mode transition by preventing shifts to lean combustion mode when battery charge is insufficient, thereby avoiding the harmful intermediate air fuel ratio condition that generates excessive NOx emissions.
Solution Approach 2:
The control device performs preliminary assessment of battery charge state before allowing transition to lean combustion mode. By checking battery charge levels in advance and preventing mode transitions when charge is insufficient, the system avoids the problematic scenario where air supply cannot be maintained at target levels, thus preventing excessive NOx emissions before they occur.
2Loss of energy
If the target air fuel ratio is set to an intermediate lean value between sufficiently lean and stoichiometric, then fuel consumption is reduced, but the engine-out NOx emission quantity increases
Solution Approach 1:
The control device changes the target air fuel ratio parameter based on battery charge state. When battery charge is insufficient, it maintains the target air fuel ratio at stoichiometric rather than allowing it to shift to intermediate lean values, thereby preventing the harmful intermediate condition while still allowing fuel-efficient lean operation when battery charge is adequate.
3Productivity
If the combustion mode is shifted to lean combustion mode, then fuel consumption is reduced, but when the battery is undercharged, the electric intake air supply device cannot maintain the target air fuel ratio, causing NOx emissions to increase
Solution Approach 1:
The control device implements feedback control by continuously monitoring battery charge state and using this information to determine whether lean combustion mode transitions are permitted. This feedback mechanism ensures that air fuel ratio control accuracy is maintained by preventing mode transitions that would compromise reliability due to insufficient battery charge.
Data Source
AI summary
A vehicular internal combustion engine system includes an internal combustion engine and an electric intake air supply device. The internal combustion engine is shifted into a stoichiometric combustion mode, and a lean combustion mode. The electric intake air supply device is driven by an on-vehicle battery, and employed to contribute a part of intake air quantity at least under a specific operating condition when in the lean combustion mode. A control method includes: determining a requested electric energy of the electric intake air supply device for a shift into the lean combustion mode in response to a shift from a stoichiometric combustion operation region into a lean combustion operation region; and continuing the stoichiometric combustion mode, without operation of the electric intake air supply device, when the on-vehicle battery is in an insufficient state of charge with respect to the requested electric energy.