Variable Displacement Engine Cylinder Reactivation Control
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Solution Overview
Problem
Variable displacement engines face challenges in reducing manifold pressure efficiently during transitions from deceleration cylinder cut-off (DCCO) to deceleration fuel shut-off (DFSO) modes, leading to fuel penalties and torque transients that affect fuel economy and drivability.
Innovation Solution
The engine controller coordinates the reactivation of cylinder fueling and valve operation by transitioning one engine bank from DCCO to DFSO while reactivating fuel and valve operation on the other bank, maintaining stoichiometry until manifold pressure is reduced, and then resuming fueling richer than stoichiometry to regenerate the catalyst, thereby limiting fuel penalties and oxygen loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If air is pumped through the engine to reduce manifold pressure during transition from DCCO to DFSO mode, then manifold pressure is reduced, but oxygen is loaded on the exhaust catalysts requiring fuel-rich regeneration that increases fuel consumption
Solution Approach 1:
The engine banks are segmented into first and second groups, allowing independent control of fuel injection and valve operation for each bank. This enables selective air pumping through one bank without oxygenating the other bank's catalyst, dividing the oxygen loading problem into manageable segments.
Solution Approach 2:
Different operational modes are applied to different engine banks: the first bank operates in DFSO mode with fuel disabled and valves active to pump down manifold pressure, while the second bank operates in DCCO mode with both fuel and valves disabled to prevent oxygen loading on its catalyst.
2Loss of energy
If cylinder valves are deactivated during DCCO mode, then pumping losses are reduced and fuel economy improves, but manifold pressure equalizes with barometric pressure causing torque transients upon reactivation
Solution Approach 1:
The first bank is reactivated in DFSO mode with valves active but fuel disabled, performing preliminary air pumping to reduce manifold pressure before full fuel injection is restored. This preliminary action prevents torque transients by establishing appropriate manifold vacuum before combustion resumes on both banks.
Solution Approach 2:
The first bank operates as an intermediary system, using its active valves to pump air and reduce manifold pressure for the entire engine system, while the second bank remains in DCCO mode. This intermediary action prepares the manifold pressure conditions for smooth reactivation of both banks.
3Reliability
If fuel is injected rich of stoichiometry to regenerate exhaust catalysts after DCCO operation, then catalyst oxygen loading is reduced, but fuel economy benefits from DCCO are undone
Solution Approach 1:
The exhaust catalyst regeneration is segmented by engine bank: only the first bank undergoes rich fuel injection for catalyst regeneration, while the second bank maintains stoichiometric operation. This limits the fuel penalty to only one bank's catalyst regeneration needs.
Solution Approach 2:
Partial catalyst regeneration is performed by enriching only one bank's fuel mixture rather than both banks. This partial action is sufficient to address the oxygen loading issue while minimizing the fuel economy penalty.
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 reduces manifold pressure efficiently without oxygen loading exhaust catalysts, improving fuel economy and emissions compliance by minimizing fuel penalties associated with catalyst regeneration.
Implementation Method 1
lowering the manifold pressure by pumping air through the reactivated cylinder valves of the first group of cylinders
Implementation Method 2
operating the second group of cylinders fueled and with all engine cylinder valves reactivated
Implementation Method 3
regenerate the catalyst by operating the first group of cylinders richer than stoichiometry
Data Source
AI summary
Methods and systems are provided for improving fuel efficiency and tailpipe emissions of a variable displacement engine. Fueling is initially disabled in cylinders selected to be deactivated while pumping air through the cylinders to an exhaust after-treatment catalyst, and then valve operation is disabled. On reactivation, if manifold vacuum is dissipated, one bank of cylinders are reactivated while the other bank is operated in DFSO with valves pumping air until manifold vacuum is reestablished.