Intake Oxygen Sensor Zero Point Calibration for EGR Control
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Solution Overview
Problem
Intake oxygen sensors in engine systems face challenges in accurately determining the zero point due to sensitivity to pressure, aging, and variations in fuel or reductants, leading to reduced measurement and control accuracy of exhaust gas recirculation (EGR).
Innovation Solution
A method is implemented to learn a reference point for intake oxygen sensors during selected engine idling conditions, adjusting EGR flow based on intake oxygen concentration and pressure corrections, which reduces the impact of aging and part-to-part variability, and compensates for the effects of purge hydrocarbons and positive crankcase ventilation gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the intake oxygen sensor is used for EGR control, then EGR measurement is achieved as a function of oxygen change, but the zero point reading deviates due to pressure sensitivity, aging, and part-to-part variability
Solution Approach 1:
The patent performs preliminary calibration of the oxygen sensor zero point under controlled engine idle conditions before normal EGR measurement operations. This preliminary action establishes a baseline reference that compensates for aging and part-to-part variability, resolving the contradiction by preparing the sensor in advance under optimal conditions.
Solution Approach 2:
The patent changes operational parameters by conducting calibration specifically during engine idle conditions at controlled intake pressures. This parameter change isolates the sensor from interfering substances like PCV and purge hydrocarbons, allowing accurate zero point determination despite the sensor's sensitivity to pressure and aging.
2Measurement precision
If calibration is performed under various engine conditions, then comprehensive sensor characterization is achieved, but sensor output is confounded by PCV and purge hydrocarbons
Solution Approach 1:
The patent applies local quality by selecting a specific operational regime (engine idle conditions) for calibration that has locally optimal properties - minimal interference from PCV and purge hydrocarbons. This localized approach to calibration resolves the contradiction by finding a specific operating window where harmful factors are minimized.
Solution Approach 2:
The patent converts the typically problematic presence of PCV and purge hydrocarbons into a benefit by identifying engine idle conditions as the optimal calibration window - precisely when these substances are minimal or absent. This transforms what could be a source of error into a opportunity for accurate calibration.
3Measurement precision
If the oxygen sensor output is corrected for pressure changes, then pressure effects are compensated, but additional correction factors and calculations are required
Solution Approach 1:
The patent implements self-service by having the control system automatically perform pressure correction calculations using readily available intake pressure sensor data. The system self-corrects the oxygen sensor output without external intervention, resolving the contradiction by making the correction process automatic and integrated into normal operation.
Solution Approach 2:
The patent uses feedback by continuously monitoring intake pressure and applying real-time corrections to the oxygen sensor output. This feedback loop ensures that pressure effects are continuously compensated, maintaining accuracy without requiring complex manual intervention.
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 control by reliably learning the zero point, reducing noise factors and pressure effects, and accounting for sensor aging and part-to-part variations, resulting in more precise EGR estimation and control.
Implementation Method 1
an oxygen sensor, which may be employed to measure oxygen
Data Source
AI summary
Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor during selected idling conditions. The learned zero point is used to infer EGR flow and accordingly adjust EGR valve control. In addition, EGR valve leakage is diagnosed based on the zero point learned during an idle adaptation relative to a zero point learned during a DFSO adaptation.