Engine Idle-Stop Starter Engagement via Controlled Brake Torque
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Solution Overview
Problem
Current engine idle-stop systems require a complete engine shutdown before restart, leading to increased change of mind restart time and degraded restart quality when a driver decides to immediately restart the engine during shutdown.
Innovation Solution
A method that adjusts brake torque applied to a deactivated engine to slow it to a predetermined threshold speed without stopping, allowing the starter to engage and restart the engine immediately, using combinations of reverse torque, transmission drag torque, and gas torque to expedite engine slow-down and restart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is required to stop completely before restart, then the starter can be reliably engaged, but the change of mind restart time is substantially increased
Solution Approach 1:
The system changes the parameter of engine speed threshold for starter engagement from zero (complete stop) to a non-zero threshold (e.g., 50 rpm or 100 rpm). This allows the starter to engage while the engine is still rotating slowly, reducing the time required for restart while maintaining reliable starter engagement through controlled deceleration to the threshold speed.
2Loss of time
If the engine is slowed down rapidly to enable quick restart, then restart time is reduced, but excessive brake torque may cause harmful effects
Solution Approach 1:
The system dynamically adjusts brake torque based on real-time engine speed and the difference between current speed and the starter engagement threshold. The brake torque is modulated to achieve smooth, controlled deceleration rather than abrupt stopping, preventing excessive torque shocks while still achieving rapid enough slowdown to enable quick restart.
Solution Approach 2:
The control system continuously monitors engine speed and uses feedback to regulate brake torque application. By comparing current engine speed with the threshold speed and adjusting brake torque accordingly, the system ensures controlled deceleration that avoids excessive harmful effects while achieving timely restart.
3Speed
If brake torque is applied to slow the engine, then the engine can be brought to threshold speed for starter engagement, but the brake system must handle additional torque load
Solution Approach 1:
The system applies brake torque partially and selectively only when needed to bridge the gap between current engine speed and the starter engagement threshold. Rather than applying maximum brake torque continuously, the system uses controlled partial braking action sufficient to achieve the threshold speed, reducing unnecessary torque load on the brake system while still enabling rapid restart capability.
Data Source
AI summary
Method and systems are provided for controlling a vehicle system including an engine that is selectively deactivated during engine idle-stop conditions. One example method comprises, adjusting a brake torque applied to a deactivated rotating engine after an engine restart request, the brake torque applied to slow the engine to at least a predetermined threshold speed without stopping the engine, and engaging a starter to the still rotating engine to increase the engine speed and restart the engine.