Intake Oxygen Sensor Compensation for EGR Control Accuracy

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Solution Overview

Problem

Intake oxygen sensor measurements for determining exhaust gas recirculation (EGR) in low-pressure EGR vehicle systems are corrupted by fuel vapors during the purging process, leading to inaccurate EGR readings, which can result in high engine temperatures, reduced fuel economy, and increased NOx emissions.

Innovation Solution

Measuring oxygen concentration during specific conditions when EGR is off and boost pressure is greater than barometric pressure, estimating purge fuel concentration, and applying a purge correction factor during EGR on conditions to correct oxygen sensor readings and accurately determine EGR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If fuel vapor purging is performed to the boosted intake side, then fuel economy is improved, but oxygen sensor measurements are corrupted leading to inaccurate EGR readings

Engineering Contradiction:

Improvefuel economyVSAvoidoxygen sensor measurement accuracy

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The system performs preliminary characterization of fuel vapor effects on oxygen sensor readings during a learned state (when EGR is off), storing this information for later compensation during EGR operation. This preliminary action allows the system to account for fuel vapor interference before it corrupts EGR measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from oxygen sensor readings during a learned state to determine a fuel concentration value, which is then used to compensate for fuel vapor interference during EGR operation. The compensation factor is adjusted based on the difference between expected and actual oxygen sensor responses.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If oxygen sensor sensitivity is reduced by fuel vapor reaction, then the sensor cannot detect actual oxygen concentration changes, but stopping purging would eliminate this interference

Engineering Contradiction:

Improveoxygen concentration detection accuracyVSAvoidfuel economy

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The system introduces a compensation factor as an intermediary element that mediates between the corrupted oxygen sensor readings and the actual EGR calculation. This compensation factor, derived from fuel concentration measurements during a learned state, allows the system to correct sensor readings without stopping purging.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the operational parameters by introducing a dynamic compensation factor that adjusts the interpretation of oxygen sensor readings based on fuel vapor concentration. This allows accurate EGR measurement despite the sensor's reduced sensitivity during purging conditions.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If EGR control is based on corrupted oxygen sensor readings, then EGR accuracy deteriorates, but the purging process should continue for fuel economy

Engineering Contradiction:

ImproveEGR measurement accuracyVSAvoidemissions

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The system uses feedback from oxygen sensor readings during a learned state (when EGR is off) to determine a fuel concentration value, which is then used to compensate for fuel vapor interference during EGR operation. The compensation factor is adjusted based on the difference between expected and actual oxygen sensor responses.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #10Preliminary action

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 method compensates for the corruption caused by fuel vapor purging, enabling accurate EGR control while allowing purging to continue, thereby improving engine performance and reducing emissions.

Implementation Method 1

An intake oxygen sensor may be located in the engine intake downstream from the compressor to provide an indication of EGR flow

Methodology Applied

Scientific EffectOxygen sensor electrochemical detection:

Implementation Method 2

The purge fuel vapors can react on the surface of the oxygen sensor element and reduce the oxygen sensor element sensitivity

Methodology Applied

Scientific EffectSurface oxidation reaction: Oxidation

Data Source

PatentUS9273602B2Intake air oxygen compensation for EGR

Publication Date: 2016.03.01 FORD GLOBAL TECH LLC

AI summary

To compensate for possible corruption in exhaust gas recirculation control caused by fuel vapor purging, while still enabling the purging to continue, an engine intake oxygen concentration may be corrected based on a fuel canister vapor purge only during boosted conditions. Responsive to the intake oxygen concentration, exhaust gas recirculation may be adjusted.