Intake Oxygen Sensor EGR Estimation via Purge Valve Modulation
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Solution Overview
Problem
Existing intake oxygen sensors in engine systems are confounded by fuel vapor and oil mist during boosted engine operation with exhaust gas recirculation (EGR), leading to inaccurate EGR estimation due to the consumption of oxygen by reductants on the sensor's catalytic surface, which can result in incorrect EGR control, affecting emissions and fuel economy.
Innovation Solution
Modulating the canister purge valve (CPV) during boosted engine operation to estimate and correct for purge flow rates based on intake oxygen sensor outputs, adjusting the EGR flow by determining the change in oxygen concentration due to purge flow and using this correction factor to isolate the EGR flow estimate, thereby improving the accuracy of EGR control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an intake oxygen sensor is used to estimate EGR during boosted engine operation, then EGR measurement capability is improved, but measurement precision deteriorates due to interference from fuel vapor and oil mist consuming oxygen on the sensor's catalytic surface
Solution Approach 1:
The patent introduces a correction routine that acts as an intermediary between the raw oxygen sensor signal and the final EGR calculation. This routine measures the oxygen consumption caused by fuel vapor and oil mist separately and subtracts it from the total oxygen consumption to isolate the EGR-related oxygen consumption, thereby eliminating the harmful interference effect
Solution Approach 2:
The patent changes the operational parameters of the purge valve (opening/closing frequency, duty cycle) to create a measurable signal that allows differentiation between oxygen consumption from purge vapors versus EGR. By modulating the purge valve and observing the corresponding oxygen sensor signal changes, the system can calculate a correction factor that compensates for the harmful effects
2Productivity
If purge flow is enabled during boosted engine operation, then fuel vapor management is improved, but EGR estimation accuracy deteriorates due to oxygen consumption by hydrocarbons in the purge stream
Solution Approach 1:
The patent implements periodic modulation of the purge valve (opening and closing at specific frequencies) to create a time-varying signal that can be distinguished from the steady-state EGR effect. This periodic action allows the control system to identify and quantify the oxygen consumption specifically attributable to purge vapors, enabling accurate correction of the EGR measurement
Solution Approach 2:
The patent uses feedback from the oxygen sensor to continuously monitor and quantify the oxygen consumption caused by purge vapors. This feedback signal is processed to generate a correction factor that is applied in real-time to compensate for the interference, allowing the system to maintain accurate EGR estimation even when purge flow is active
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 enhances the accuracy of EGR estimation and control, reducing engine emissions and improving fuel economy by accounting for the confounding effects of purge flow on the intake oxygen sensor, ensuring precise EGR delivery.
Implementation Method 1
an intake oxygen sensor coupled to the intake manifold downstream of the charge air cooler and upstream of the intake throttle
Implementation Method 2
the sensor may be sensitive to the presence of fuel vapor and other reductants and oxidants such as oil mist. For example, during boosted engine operation, purge air may be received at a compressor inlet location. Hydrocarbons ingested from purge air, positive crankcase ventilation (PCV) and/or rich EGR can consume oxygen on the sensor catalytic surface
Data Source
AI summary
Methods and systems are provided for estimating a fuel canister purge flow based on outputs of an intake manifold oxygen sensor. For example, during boosted engine operation when exhaust gas recirculation (EGR) is flowing below a threshold and purge is enabled, purge flow may be estimated based on changes in the sensor output while modulating a canister purge valve between an open and closed position. Then, during subsequent operation wherein EGR and purge flow are enabled, the output of the sensor may be adjusted based on the estimated purge flow.