Variable Displacement Engine Knock Control via Cylinder State Segmentation
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Solution Overview
Problem
Variable displacement engines face fuel economy losses due to excessive ignition timing retard applied to multiple cylinders to mitigate knock, which negates the benefits of cylinder deactivation.
Innovation Solution
Adjusting ignition timing differently based on the operational state of the engine, allowing individual cylinder knock control during partial cylinder operation and global knock control during full cylinder operation, to minimize fuel economy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple cylinders' ignition timing is retarded to abate knock during partial cylinder operation, then knock is reduced, but fuel economy losses increase greater than the fuel economy gained by VDE operation
Solution Approach 1:
The patent segments the knock control approach by cylinder operational state: during partial cylinder operation, only the selected active cylinder's ignition timing is adjusted in response to knock indications, whereas during full cylinder operation, multiple cylinders' ignition timing is adjusted. This segmentation allows precise control that avoids unnecessary retardation of inactive cylinders, thereby preserving fuel economy benefits while maintaining reliable knock control.
2Loss of energy
If individual cylinder knock control is implemented during partial cylinder operation, then fuel economy benefits are retained, but the complexity of determining which cylinder is knocking increases
Solution Approach 1:
The patent implements dynamic adjustment of knock control strategy based on engine operational mode. The control system transitions between individual cylinder knock control during partial cylinder operation and multi-cylinder knock control during full cylinder operation. This dynamic approach optimizes the balance between fuel economy and control complexity by adapting the control granularity to the current operational context.
Solution Approach 2:
The patent changes the control parameter scope based on operational state: during partial cylinder operation, the system uses cylinder-specific knock control parameters for the active cylinder only, while during full cylinder operation, it uses aggregated knock control parameters across multiple cylinders. This parameter adaptation allows the system to maintain fuel economy benefits when cylinders are deactivated while simplifying the control algorithm.
Data Source
AI summary
Systems and methods for adjusting ignition timing to one or more cylinders of a variable displacement engine responsive to a knock indication are described herein. In one particular example, during a partial cylinder mode, ignition timing to one or more cylinders may be adjusted responsive to a knock indication based on the number of cylinders deactivated; whereas during the full cylinder mode, ignition timing for all cylinders are adjusted responsive to a knock indication. Thereby, the systems and methods described allow a larger partial cylinder operating window that has a benefit of enhancing a vehicle's fuel economy.