Dynamic Valve Timing for Skip Fire NVH Control
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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 noise, vibration, and harshness (NVH) levels increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting valve timing parameters (intake valve closing timing, exhaust valve opening timing) to create different gas spring characteristics (low pressure exhaust spring, high pressure exhaust spring, air spring) in skipped cycles. This resolves the NVH problem while maintaining skip fire fuel economy benefits by changing the physical parameters of the trapped gas rather than the engine structure itself.
Solution Approach 2:
The invention implements dynamics by making the gas spring type variable and adjustable in real-time based on operating conditions. The controller dynamically selects between different gas spring types (low pressure exhaust spring, high pressure exhaust spring, air spring) for different skipped cycles, transforming the static skip fire control into a dynamic system that can 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 levels are reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by using the existing variable valve timing mechanism to perform multiple functions: it controls both the gas exchange process and creates different gas spring types for NVH control. The same valve timing adjustments that optimize combustion also create the desired gas spring characteristics, eliminating the need for separate NVH control mechanisms and reducing overall device complexity.
Solution Approach 2:
The invention implements self-service by using the trapped exhaust gas and air already present in the cylinder to create the gas spring effect. The system utilizes existing materials (exhaust gas, air) and existing mechanical movements (piston motion, valve timing) to generate the cushioning effect, rather than requiring external gas springs or additional active control systems.
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 NVH levels and improves fuel economy by optimizing the gas spring type in skipped cycles, leading to a smoother engine operation and reduced vibrations.
Implementation Method 1
The trapped gases form different types of 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.