Engine Cylinder Deactivation with Variable Piston Displacement
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Solution Overview
Problem
Existing engine systems with variable cylinder deactivation face limitations in compression ratio range at part load operations, leading to fuel penalties and knock constraints, particularly due to the need for high-octane fuels to prevent combustion detonation.
Innovation Solution
Implementing a method that coordinates selective cylinder deactivation with variable piston displacement to adjust compression ratios of active cylinders, maintaining spark timing at peak torque timing, and reducing engine thermal and pumping losses by synchronizing deactivation with compression ratio adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cylinders are grouped based on compression ratio for selective deactivation, then fuel economy is improved through reduced pumping losses, but the range of compression ratios available at part load operation is limited
Solution Approach 1:
The patent applies dynamics by making the compression ratio adjustable in real-time through variable displacement pistons. Instead of fixed compression ratio groups, the system dynamically changes the compression ratio of active cylinders based on operating conditions, allowing continuous adaptation rather than discrete group-based selections.
Solution Approach 2:
The system changes the compression ratio parameter dynamically by adjusting piston displacement positions. This allows the compression ratio to be varied continuously rather than being fixed in discrete groups, enabling finer control over engine performance and fuel economy across different operating conditions.
2Use of energy by moving object
If high compression ratio cylinders are deactivated at part load to improve fuel economy, then pumping losses are reduced, but knock constraints require lower compression ratios to be used
Solution Approach 1:
The system dynamically adjusts compression ratio in real-time based on knock detection and operating conditions. When knock is detected, the compression ratio of active cylinders is reduced immediately, allowing the engine to maintain fuel economy benefits while preventing knock damage.
Solution Approach 2:
The system uses knock sensors to provide feedback on combustion conditions. This feedback loop allows the control system to detect knock events and adjust the compression ratio of active cylinders accordingly, balancing fuel economy improvement with knock prevention.
3Object-affected harmful factors
If spark timing is retarded to address knock, then combustion detonation is prevented, but fuel economy deteriorates due to loss of peak torque timing
Solution Approach 1:
The system dynamically adjusts compression ratio to allow spark timing to remain at peak torque timing even under knock-prone conditions. By changing the compression ratio in real-time, the system prevents knock without sacrificing the optimal spark timing for fuel economy.
Solution Approach 2:
The system changes the compression ratio parameter to manage knock instead of changing spark timing. This allows spark timing to remain at the optimal peak torque timing for fuel economy while the compression ratio adjustment prevents combustion knock.
Data Source
AI summary
Methods and systems are provided for coordinating cylinder deactivation adjustments with changes to individual cylinder piston displacement. In doing do, the benefits of variable displacement and variable compression ratio may be synergized. An engine can be operated with some cylinders deactivated while active cylinders operate with knock addressed while spark timing is at MBT for a longer duration.