Skip Fire Engine Actuator Coordination for NVH Reduction

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 the cam phase is adjusted in stages to intermediate targets, allowing for gradual changes in firing fractions, thereby maintaining optimal air charge and reducing NVH and fuel efficiency losses during transitions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If firing fraction transitions are implemented in skip fire engines, then fuel efficiency is improved, but NVH performance deteriorates during transitions

Engineering Contradiction:

Improvefuel efficiencyVSAvoidNVH performance

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The cam phase is adjusted to intermediate targets before the firing fraction transition is completed. This preliminary action prepares the air charge system in advance, allowing the transition to proceed more smoothly and reducing NVH disturbances during the firing fraction change.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The cam phase adjustment is divided into multiple intermediate targets rather than a single direct transition. This segmentation allows the system to progress through staged adjustments, maintaining better control over air charge and reducing NVH impacts during each incremental step of the firing fraction transition.

Inventive Principle:

Principle #1Segmentation

2Speed

If cam phase is adjusted rapidly during firing fraction transitions, then transition speed is improved, but air charge optimization deteriorates

Engineering Contradiction:

Improvetransition speedVSAvoidair charge optimization

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The cam phase adjustment is divided into multiple intermediate targets rather than a single direct transition. This segmentation allows the system to progress through staged adjustments, maintaining better control over air charge and reducing NVH impacts during each incremental step of the firing fraction transition.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cam phase is adjusted to intermediate targets before the firing fraction transition is completed. This preliminary action prepares the air charge system in advance, allowing the transition to proceed more smoothly and reducing NVH disturbances during the firing fraction change.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If staged cam first transition strategy is used, then NVH is reduced, but transition complexity increases

Engineering Contradiction:

ImproveNVHVSAvoidtransition control complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The cam phase adjustment is divided into multiple intermediate targets rather than a single direct transition. This segmentation allows the system to progress through staged adjustments, maintaining better control over air charge and reducing NVH impacts during each incremental step of the firing fraction transition.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10094313B2Coordination of vehicle actuators during firing fraction transitions

Publication Date: 2018.10.09 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or other 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.