Variable Displacement Engine Knock Control via Dynamic Threshold Adjustment

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Solution Overview

Problem

Variable displacement engines (VDEs) face challenges in reliable engine knock detection due to changes in cylinder firing density, leading to false indications of engine knock, which can degrade engine performance and fuel economy.

Innovation Solution

The method involves adjusting fuel injector control actions and cylinder firing density to maintain consistent engine knock background noise levels during VDE mode changes, using a controller to manage fuel injection timing and cylinder activation to reduce false knock indications and improve detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If cylinders are deactivated to improve fuel economy, then fuel economy is improved, but engine knock background noise levels change causing false knock indications

Engineering Contradiction:

Improvefuel economyVSAvoidknock detection reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system dynamically adjusts the knock detection threshold based on the current VDE mode. When cylinders are deactivated, the controller recognizes the changed background noise level and adjusts the threshold accordingly, allowing the system to maintain reliable knock detection across different operational states while preserving fuel economy benefits

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The controller changes the knock detection parameter (threshold) based on the operational mode. By detecting whether the engine is in a VDE mode with deactivated cylinders, the system modifies the threshold to account for the different background noise characteristics, thereby maintaining detection accuracy regardless of the fuel economy optimization state

Inventive Principle:

Principle #35Parameter changes

2Productivity

If cylinders are deactivated to increase engine efficiency, then engine efficiency is improved, but false knock indications increase

Engineering Contradiction:

Improveengine efficiencyVSAvoidfalse knock indications

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The controller proactively adjusts the knock detection threshold before false knock indications can occur. By anticipating the change in background noise when cylinders are deactivated and pre-adjusting the threshold, the system prevents false indications rather than reacting to them after they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from the operational state (detected VDE mode) to continuously adapt the knock detection threshold. This closed-loop approach ensures that the threshold always reflects the current background noise level, eliminating false knock indications while maintaining the efficiency benefits of cylinder deactivation

Inventive Principle:

Principle #23Feedback

3Reliability

If spark timing is retarded to control engine knock, then engine knock is controlled, but fuel economy deteriorates

Engineering Contradiction:

Improveengine knock controlVSAvoidfuel economy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system replaces the mechanical approach of retarding spark timing with an electronic/software-based solution. By substituting the physical spark timing adjustment with an electronic threshold adjustment in the knock detection algorithm, the system achieves knock control without the fuel economy penalty associated with retarded spark timing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11204011B2Method and system for variable displacement engine knock control

Publication Date: 2021.12.21 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine background noise levels for detecting engine knock may be the basis for determining whether or not the engine is operating in a cylinder deactivation mode. Further, select variable engine displacement modes may be avoided so that engine background noise level changes may be reduced to improve engine knock detection.