Engine Restart Control via Cylinder Air Charge Segmentation
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Solution Overview
Problem
Vehicles with start/stop technology face a conflict between rapid engine restarting and comfortable engine rundown due to the need for varying air charges in the cylinders, leading to delays and inconvenience in 'change-of-mind' situations.
Innovation Solution
The method involves using an air metering device to manage air charges in cylinders, predicting engine speed thresholds to determine optimal times for starter engagement, allowing for rapid and efficient restarting by adjusting the throttle valve and camshaft settings to control air flow and fuel injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the throttle valve is closed during engine rundown to reduce air charge in cylinders, then vibration is suppressed and rundown comfort is improved, but the ability to rapidly restart the engine is degraded due to insufficient air charge
Solution Approach 1:
The invention divides the engine cylinders into different groups with different air charge levels during rundown. Some cylinders (first cylinders) receive reduced air charge to minimize vibration, while other cylinders (second cylinders) maintain or receive increased air charge to enable rapid restart. This segmentation allows simultaneous optimization of both rundown comfort and restart capability.
Solution Approach 2:
Different air charge conditions are applied to different locations (cylinders) within the engine system. The throttle valve is controlled to create localized air charge differences: restricted airflow to certain cylinders for comfort, while ensuring adequate airflow to specific cylinders for restart readiness.
2Ease of manufacture
If the engine is allowed to come to a halt before restarting, then restart preparation is simplified, but delays occur in change-of-mind situations reducing restarting rapidity
Solution Approach 1:
The system performs preliminary preparation for potential restart while the engine is still running down. The control device monitors engine speed and identifies optimal restart opportunities before the engine comes to a complete halt, allowing the starter to be engaged at the most favorable moment rather than waiting for shutdown.
Solution Approach 2:
The restart strategy is made dynamic rather than static. Instead of always waiting for complete shutdown, the system adaptively determines restart timing based on real-time engine speed and predicted rundown behavior, engaging the starter when conditions are most favorable for rapid restart.
3Ease of operation
If the air charge in all cylinders is reduced during rundown, then vibration is minimized, but the complexity of control increases to manage differential air charging
Solution Approach 1:
The existing throttle valve and engine control unit are made multi-functional. The throttle valve not only controls overall engine airflow but also enables differential air charging between cylinder groups. The control unit performs both standard engine management functions and the additional task of predicting rundown behavior and determining optimal restart timing.
Data Source
AI summary
The invention relates to a method for restarting an internal combustion engine, in which a first cylinder (ZYL1) has a low air level and a second cylinder (ZYL2) has a high air level, and wherein a predefined speed threshold value (ns) is selected as a function of said air levels. A method for the restart is selected and carried out as a function of a comparison of the determined speed (n) of the internal combustion engine with the predefined speed threshold value (ns).