Skip-Firing Engine Intake Valve Dynamics
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Solution Overview
Problem
Skip-firing in internal combustion engines leads to increased pumping losses and reduced efficiency due to intake valves remaining closed during compression and power strokes in skipped cylinders, and at low fueling levels, fuel injectors become inaccurate, causing higher emissions and unstable engine operation.
Innovation Solution
Implement a method where the engine controller determines when to skip-fire based on fueling demands and engine speed, and uses secondary electromagnetic actuators to hold open the intake valves of skipped cylinders for a longer duration than those of firing cylinders, reducing pumping losses and improving fuel injection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If skip-firing is implemented to reduce emissions during engine idling, then emissions are reduced, but pumping losses increase due to intake valves remaining closed during compression stroke
Solution Approach 1:
The patent applies dynamics by making the intake valve timing variable rather than fixed. A secondary actuator dynamically adjusts the intake valve closing timing based on whether the cylinder is firing or skipped, allowing the valve to remain open longer during compression stroke in skipped cylinders to reduce pumping losses while maintaining emission reduction benefits
2Use of energy by moving object
If fuel injection amount is reduced at low fueling demands, then fuel economy improves, but fuel injector accuracy decreases leading to larger metering errors
Solution Approach 1:
The patent applies parameter changes by skipping fuel injection in certain cylinders under low fueling demand conditions. This changes the operating parameters of the fuel injection system, allowing firing cylinders to receive adequate fuel amounts for accurate injection while skipped cylinders consume no fuel, thereby maintaining both fuel economy and injection accuracy
3Use of energy by moving object
If skip-firing is used to improve fuel economy, then fuel consumption decreases, but engine speed stability deteriorates due to fluctuations beyond acceptable range
Solution Approach 1:
The patent applies local quality by selectively applying skip-firing to specific cylinders rather than uniformly across all cylinders. The controller identifies which cylinders should be skipped based on operating conditions, allowing some cylinders to fire and provide stable torque while others are skipped for fuel economy, thus maintaining overall engine speed stability
Solution Approach 2:
The patent applies feedback by using the engine controller to monitor engine operating conditions and dynamically adjust skip-firing strategies. The controller receives feedback on engine speed, load, and other parameters to determine when and which cylinders to skip, ensuring engine speed remains within acceptable ranges while achieving fuel economy benefits
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 emissions, stabilizes engine operation, and increases efficiency by maintaining fuel injectors in their non-ballistic regions, even at low engine speeds, while minimizing pumping losses and extending intake valve opening during compression and power strokes.
Implementation Method 1
uses secondary electromagnetic actuators to hold open the intake valves of skipped cylinders
Implementation Method 2
maintaining fuel injectors in their non-ballistic regions
Data Source
AI summary
Various methods and systems are provided for skip-firing an engine. As one embodiment, a method for an engine includes firing all cylinders of the engine and not altering the closing timing of the intake valves when fueling demands are greater than a threshold. The method further includes skip-firing the engine when fueling demands are less than a threshold, and holding open the intake valves of skipped cylinders for a greater duration than intake valves of firing cylinders.