Intake Oxygen Sensor EGR Correction

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Solution Overview

Problem

Existing intake oxygen sensors in engine systems face inaccuracies in EGR estimation due to rich or lean EGR conditions, leading to misrepresentations of engine operating parameters, which can disrupt fueling and EGR control.

Innovation Solution

A method that corrects the intake manifold oxygen sensor output with a correction factor based on the EGR air-fuel ratio and ethanol content, adjusting EGR rate and fuel injection to account for rich or lean conditions, and uses uncorrected sensor output for spark timing and airflow adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the intake oxygen sensor is used to measure EGR during rich EGR conditions, then the sensor output is affected by excess fuel reacting with oxygen and H2 diffusion, but the sensor can still detect oxygen concentration changes

Engineering Contradiction:

ImproveEGR estimation accuracyVSAvoidsensor output reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

An exhaust gas oxygen sensor is introduced as an intermediary device to measure the air-fuel ratio of EGR gas. This mediator provides accurate information about EGR composition (rich or lean conditions) so that the intake oxygen sensor output can be properly interpreted and corrected, resolving the reliability issue without sacrificing the measurement capability of the intake sensor.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses feedback from the exhaust gas oxygen sensor to continuously monitor EGR air-fuel ratio conditions. Based on this feedback, the controller applies correction factors to the intake oxygen sensor output, allowing accurate EGR estimation even when the intake sensor output is affected by rich or lean EGR conditions.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the intake oxygen sensor output is corrected for rich EGR conditions, then EGR estimation accuracy improves, but engine operating parameters such as spark timing, throttle position, and fuel injection may be incorrectly adjusted

Engineering Contradiction:

ImproveEGR estimation accuracyVSAvoidengine control accuracy

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The control system segments the correction application by function: the intake oxygen sensor output is corrected only for EGR estimation purposes, while uncorrected output is retained for controlling engine operating parameters. This segmentation allows accurate EGR measurement without compromising the accuracy of spark timing, throttle, and fuel injection control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different quality corrections are applied to different uses of the sensor data. The corrected sensor output (compensated for rich/lean EGR effects) is used locally for EGR estimation, while the uncorrected output is used locally for engine control decisions. This local quality approach ensures each function receives the appropriate data quality.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If the intake oxygen sensor is positioned downstream of the EGR passage outlet, then the sensor can measure EGR dilution, but the sensor becomes sensitive to EGR air-fuel ratio variations

Engineering Contradiction:

ImproveEGR dilution measurementVSAvoidEGR air-fuel ratio sensitivity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The exhaust gas oxygen sensor serves as an intermediary that measures the EGR air-fuel ratio independently. This intermediary measurement allows the system to compensate for the harmful sensitivity effect, enabling the intake oxygen sensor to remain in the optimal downstream position for EGR dilution measurement while correcting for air-fuel ratio variations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sensitivity of the intake oxygen sensor to EGR air-fuel ratio variations, which is initially a harmful effect, is converted into a beneficial indicator. By monitoring these variations with the exhaust gas oxygen sensor, the system can apply appropriate correction factors, turning the sensitivity issue into a source of additional information for improving measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach improves the accuracy of EGR dilution estimation, reduces fuel system errors, and enhances open and closed-loop fuel and spark control, ensuring more precise engine operation across varying EGR conditions.

Implementation Method 1

an oxygen sensor, which may be employed during non-EGR conditions to determine the oxygen content of fresh intake air

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 2

smaller H2 molecules diffusing faster through the diffusion barrier of the oxygen sensor's sensing element

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9518529B2Methods and systems for an intake oxygen sensor

Publication Date: 2016.12.13 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for correcting an EGR rate determined based on an intake manifold oxygen sensor based on an air-fuel ratio of EGR. The output of the sensor is corrected to compensate for extra fuel in rich EGR or extra air in lean EGR and used to reliably estimate the EGR rate. One or more engine operating parameters are adjusted based on an uncorrected output of the sensor.