Skip Fire Actuator Coordination for NVH Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing engine control methods face challenges in managing smooth transitions between different firing fractions in skip fire and dynamic firing level modulation engines, leading to undesirable noise, vibration, and harshness (NVH) issues, while also affecting fuel efficiency and drivability.
Innovation Solution
The implementation of a staged, cam-first transition strategy, where larger firing fraction changes are broken into smaller steps with intermediate target firing fractions, allowing for concurrent adjustment of cam phase and torque converter slip to maintain optimal engine output and reduce NVH during transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If larger firing fraction changes are implemented directly, then transition speed is improved, but NVH performance deteriorates
Solution Approach 1:
The patent divides a large firing fraction change into multiple smaller intermediate steps. Instead of transitioning directly from one firing fraction to another, the system passes through intermediate firing fractions, breaking the transition into manageable segments that reduce NVH while maintaining reasonable transition speed.
Solution Approach 2:
The patent adjusts cam phase and torque converter slip in advance before implementing the firing fraction change. By preliminarily adjusting these related actuators, the system prepares the engine state to better accommodate the upcoming firing fraction transition, reducing NVH disturbances.
2Object-affected harmful factors
If multiple actuators are adjusted during transitions, then NVH performance is improved, but device complexity increases
Solution Approach 1:
The patent combines the control of multiple actuators (firing fraction, cam phase, torque converter slip) into a coordinated transition strategy. By merging these control actions and synchronizing them, the system achieves NVH reduction without proportionally increasing control complexity, as the actuators work together in an integrated manner.
Solution Approach 2:
The patent uses cam phase and torque converter slip as intermediary actuators to mediate the transition between different firing fractions. These intermediaries help smooth out the effects of firing fraction changes, reducing NVH while the control system manages them through coordinated adjustment rather than independent complex control.
3Use of energy by moving object
If cam phase and torque converter slip are adjusted concurrently, then fuel efficiency is improved, but control complexity increases
Solution Approach 1:
The patent adjusts cam phase and torque converter slip in advance before the firing fraction change is fully implemented. This preliminary adjustment of related actuators optimizes the engine state for the upcoming transition, improving fuel efficiency by reducing transient losses while the control coordination complexity is managed through the structured transition strategy.
Solution Approach 2:
The patent implements dynamic adjustment of cam phase and torque converter slip during the firing fraction transition. Rather than fixed adjustments, the system dynamically modifies these parameters in response to the transition progress, improving fuel efficiency by optimizing engine operation throughout the transition while adapting control complexity to the actual transition needs.
Data Source
AI summary
A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or dynamic firing level modulation operation of an engine. In general, actuator first transition strategies are described in which an actuator position (e.g., cam phase, TCC slip, etc.) is changed to, or close to a target position before a corresponding firing fraction change is implemented. When the actuator change associated with a desired firing fraction change is relatively large, the firing fraction change is divided into a series of two or more firing fraction change steps. A number of intermediate target selection schemes are described as well.