Variable Displacement Engine Cylinder Deactivation Control
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Solution Overview
Problem
Variable displacement engines face challenges in maintaining emissions compliance during cylinder deactivation operations, as deactivating cylinder valves interferes with on-board diagnostic routines, making it difficult to diagnose exhaust catalysts and oxygen sensors effectively.
Innovation Solution
The engine controller disables fuel to cylinders while maintaining valve operation during decreased torque demand, allowing air to flow through deactivated cylinders for diagnostic purposes, and transitions to full cylinder valve deactivation only after completing diagnostics, ensuring emissions compliance and fuel economy benefits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cylinder valves are deactivated during low torque demand, then fuel economy is improved, but on-board diagnostic routines cannot be completed
Solution Approach 1:
The patent segments the cylinder deactivation process into two distinct phases: DFSO (deceleration fuel shut-off) where only fuel injection is stopped while valves remain active, and DCCO (deceleration cylinder cut-off) where both fuel and valve operation are stopped. This segmentation allows the system to perform diagnostics during the DFSO phase when air still flows through the cylinders, then transition to full DCCO deactivation for maximum fuel economy once diagnostics are complete.
Solution Approach 2:
The patent performs on-board diagnostic routines as a preliminary action before implementing full cylinder valve deactivation. By completing the catalyst and oxygen sensor diagnostics during the DFSO phase when air flow is still present, the system ensures emissions compliance is verified before transitioning to the more aggressive DCCO mode that provides superior fuel economy benefits.
2Loss of energy
If cylinder valves are deactivated, then fuel economy is improved, but oxygen sensors and catalysts cannot be diagnosed
Solution Approach 1:
The patent segments the deactivation process into DFSO and DCCO phases, ensuring that during DFSO when diagnostics are performed, the intake and exhaust valves remain active to allow air flow through the cylinders. This maintains the ability to detect and measure oxygen sensor and catalyst performance while still achieving fuel economy benefits through fuel shut-off.
Solution Approach 2:
The patent uses the DFSO state as an intermediary condition between full operation and full DCCO deactivation. During this intermediary state, air flow is maintained through the cylinders (enabling diagnostics) while fuel is shut off (providing partial fuel economy benefit), serving as a bridge that allows both diagnostic and fuel economy objectives to be partially achieved simultaneously.
3Loss of energy
If DFSO is implemented, then fuel economy is improved, but air flow needed for diagnostics is reduced
Solution Approach 1:
The patent segments the deactivation strategy into two modes: DFSO where fuel is shut off but valves remain active maintaining air flow for diagnostics, and DCCO where both fuel and valves are deactivated for maximum fuel economy. This segmentation allows the system to select the appropriate mode based on whether diagnostics are currently being performed.
Solution Approach 2:
The patent maintains continuous air flow through the cylinders during the DFSO phase by keeping the intake and exhaust valves active, ensuring that the diagnostic process can complete without interruption. This continuous air flow enables the oxygen sensors and catalysts to be properly tested while still achieving fuel economy benefits from fuel shut-off.
Data Source
AI summary
Methods and systems are provided for improving fuel efficiency, monitor completion, 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 oxygen sensor. Once the sensor shows a lean response and catalyst monitoring is completed, cylinder valve operation is also disabled to reduce pumping losses and prevent further oxygen saturation of exhaust components.