Internal Combustion Engine Stop-Start Torque Control
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Solution Overview
Problem
In stop/start operation of internal combustion engines, existing methods face challenges in controlling torque reduction and synchronization of fuel injection and ignition, leading to issues like wall film formation, inadequate torque buildup, and increased pollutant emissions during restart.
Innovation Solution
A method that reduces torque by continuing fuel injection below a predetermined idle speed, switching off fuel injection only when specific conditions are met, such as reaching a minimum speed or exceeding uneven running limits, allowing for controlled speed reduction and flexible restart, using variations in ignition time or fuel quantity to manage torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fuel injection is switched off immediately to reduce fuel consumption, then fuel efficiency improves, but torque buildup becomes inadequate and the engine may stall
Solution Approach 1:
The control device prepares for engine restart by maintaining fuel injection at a reduced rate during the coasting phase, ensuring that fuel is already available in the combustion chamber when restart is needed, thus avoiding stall conditions while still achieving fuel savings
Solution Approach 2:
The fuel injection rate is dynamically adjusted based on engine speed and load conditions during stop/start operation, transitioning from full injection during normal operation to reduced injection during coasting, and back to full injection during restart to balance fuel consumption and engine stability
2Speed
If torque is reduced quickly to enable faster shutdown, then shutdown speed improves, but synchronization of fuel injection and ignition becomes difficult and wall film formation increases
Solution Approach 1:
The control device continuously monitors engine parameters such as crankshaft position, fuel injection timing, and ignition timing, using feedback loops to maintain precise synchronization even as engine speed changes rapidly during the coasting and shutdown phases
Solution Approach 2:
The control device adjusts multiple parameters simultaneously including fuel injection timing, ignition timing, and injection quantity in a coordinated manner during the transition phase, changing these parameters progressively to maintain optimal synchronization and combustion conditions throughout the shutdown process
3Reliability
If fuel injection continues at full rate during coasting, then torque buildup is sufficient, but fuel consumption increases and emissions rise
Solution Approach 1:
The control device applies partial fuel injection during the coasting phase rather than full injection, providing just enough fuel to maintain minimal torque availability and prevent stall while significantly reducing the total fuel consumed and associated emissions during the transition period
Data Source
AI summary
In a method for controlling an internal combustion engine (1) for a motor vehicle in stop-start operation, the internal combustion engine (1) is operated in the idling operating state. If there is a request for switch-off of the internal combustion engine (1) the torque produced by the internal combustion engine (1) is reduced while fuel continues to be injected. The fuel injection is switched off if the speed of the internal combustion engine (1) reaches a predetermined minimum value. The torque produced by the internal combustion engine (1) is increased again if the request for switching off the internal combustion engine (1) is canceled before the minimum speed is reached.