Engine Torque Control During DFSO Exit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for exiting deceleration fuel shut-off (DFSO) conditions in engines often result in undesirable torque bumps due to rich air-fuel ratios, which can cause engine stalls and affect drivability.
Innovation Solution
The engine is fueled using compression stroke direct injection until a peak torque threshold is reached, then the separation between compression stroke direct injection timing and spark timing is increased until a higher torque threshold is achieved, transitioning to intake stroke direct injection to maintain a more homogeneous air-fuel mixture and reduce torque bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compression stroke direct injection is used during DFSO exit with rich air-fuel ratio to increase exhaust catalyst efficiency, then catalyst efficiency is improved, but torque bump increases and engine stalls may occur
Solution Approach 1:
The fuel injection process is segmented into multiple phases: initial compression stroke DI to establish baseline torque, followed by a transition phase where DI timing is adjusted, and finally intake stroke DI for homogeneous mixing. This segmentation allows the system to achieve rich AFR for catalyst efficiency while controlling torque bump through phased injection strategies.
Solution Approach 2:
The injection timing is made dynamic by adjusting the separation between compression stroke DI and spark event based on real-time torque feedback. The controller increases separation when torque approaches peak and decreases separation when torque drops, creating a dynamic response that maintains catalyst efficiency while minimizing torque bump.
2Power
If compression stroke direct injection timing is advanced to increase torque output during DFSO exit, then torque output is improved, but engine stalls may occur
Solution Approach 1:
The system employs feedback control by monitoring engine torque during DFSO exit and dynamically adjusting compression stroke DI timing based on whether torque is increasing or decreasing. When torque approaches peak, the controller increases separation between injection and spark; when torque drops, it decreases separation. This feedback mechanism prevents engine stalls while maintaining adequate torque output.
Solution Approach 2:
The injection timing parameter is changed dynamically during DFSO exit by adjusting the crank angle separation between compression stroke DI and spark event. This parameter change allows the system to optimize torque output at different phases of the DFSO exit, preventing stalls while maintaining power.
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 prevents engine stalls and provides a smoother torque transition during DFSO exit, enhancing drivability and reducing emissions by maintaining a stoichiometric air-fuel ratio.
Implementation Method 1
fueling an engine via a compression stroke direct injection (DI)
Implementation Method 2
separation between the compression stroke DI and the spark event
Data Source
AI summary
Methods and systems are provided for fueling an engine of a vehicle during an exit from a deceleration fuel shut-off (DFSO) condition. In one example, a method may include fueling the engine using a compression stroke direct injection during the exit from the DFSO condition to reach a first engine torque threshold, and may further include increasing a separation between the compression stroke direct injection and a spark to gradually increase the engine torque to a second, higher engine torque threshold, and thereafter transitioning engine fueling from the compression stroke direct injection to an intake stroke direct injection. In this way, torque bumps may be reduced during DFSO exit.