Skip Fire Phase Transition Controller for Engine NVH Reduction
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Solution Overview
Problem
Skip fire engine control systems face challenges in managing firing sequence phase transitions, particularly when transitioning from dynamic skip fire to fixed cylinder-based firing patterns, which can result in undesirable noise, vibration, and harshness (NVH) issues during transitions.
Innovation Solution
The implementation of a first-order sigma delta converter-based controller that adjusts the firing sequence phase by adding an offset value to an accumulator, allowing for dynamic alteration of the firing sequence to match a desired phase, thereby smoothing transitions and reducing NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic skip fire control is used to achieve finer control of effective engine displacement, then adaptability is improved, but noise, vibration, and harshness (NVH) worsen during phase transitions
Solution Approach 1:
The system detects when a firing sequence phase transition is needed and proactively adjusts the phase before the transition occurs. The controller monitors the firing sequence and predetermined phase values, then implements phase adjustment by modifying which cylinders fire in upcoming cycles, preventing NVH issues rather than reacting to them after they occur.
Solution Approach 2:
The system dynamically adjusts the firing sequence phase based on real-time operating conditions. The controller continuously monitors engine operation and modifies the firing pattern phase adaptively, allowing the system to transition smoothly between different effective displacement modes while maintaining optimal NVH characteristics across varying operating conditions.
2Ease of operation
If firing sequence phase is adjusted dynamically, then drivability is improved, but device complexity increases
Solution Approach 1:
The controller implements a feedback mechanism that monitors the current firing sequence phase and compares it against predetermined phase values associated with different effective displacement modes. Based on this feedback, the controller automatically adjusts the firing sequence phase by selecting appropriate cylinder firing patterns, enabling smooth transitions without requiring complex manual intervention or additional hardware.
Data Source
AI summary
Methods and controllers for dynamically altering the phase of a firing sequence during operation of an engine are described. The described methods and controllers are particularly useful in conjunction with dynamic skip fire operation of the engine.