Dynamic Valve Control for Skip Fire Engine NVH
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Solution Overview
Problem
Skip fire engine control systems face challenges in managing noise, vibration, and harshness (NVH) issues, which have hindered their widespread adoption despite potential benefits in fuel economy.
Innovation Solution
The system modifies the timing of cylinder intake and exhaust events to create different types of gas springs in skipped working cycles, optimizing fuel efficiency and NVH levels by varying the gas spring type, such as low pressure exhaust spring, high pressure exhaust spring, or air spring, and adjusting fuel injection and ignition timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If skip fire engine control is implemented to improve fuel economy, then fuel efficiency is improved, but NVH (noise, vibration and harshness) increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting valve timing parameters (intake valve closing timing, exhaust valve opening timing) to control the type and pressure of gas springs in skipped cycles. This resolves the NVH issue while maintaining fuel economy benefits by optimizing the thermodynamic parameters of skipped cycles rather than simply deactivating cylinders.
Solution Approach 2:
The patent implements dynamics by making the valve timing adjustable and variable based on operating conditions. The intake and exhaust valve timing is dynamically modified to create different gas spring types (low pressure, medium pressure, high pressure) depending on the skip fire pattern and engine load, allowing the system to adapt to minimize NVH while maintaining fuel efficiency.
2Object-affected harmful factors
If valve timing is modified to create different gas spring types, then NVH is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by using the existing intake and exhaust valves for dual purposes: their primary function of gas exchange and their secondary function of creating controlled gas springs during skipped cycles. The same valve timing mechanism serves multiple functions (cylinder deactivation, gas spring creation, NVH control) without requiring additional dedicated components.
Solution Approach 2:
The patent implements self-service by utilizing the trapped exhaust gases and intake air already present in the cylinder to form gas springs that provide the beneficial cushioning effect. The system uses the engine's own operating conditions (exhaust gas pressure, intake manifold pressure) to create the gas springs without requiring external power sources or additional mechanical components.
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 effectively reduces NVH and improves fuel economy by optimizing the gas spring type in skipped cycles, leading to smoother engine operation and reduced vibrations.
Implementation Method 1
the gases trapped have different masses and constituent components, effectively forming gas springs during the skipped working cycle(s)
Data Source
AI summary
Various methods and arrangements for improving fuel economy and noise, vibration, and harshness (NVH) in a skip fire controlled engine are described. An engine controller dynamically selects a gas spring type for a skipped firing opportunity. Determination of the skip/fire pattern and gas spring type may be made on a firing opportunity by firing opportunity basis.