Throttle Control Using Oxygen Sensor Dilution Threshold
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Solution Overview
Problem
Existing engine systems face issues with overestimating exhaust gas recirculation (EGR) due to the presence of water vapor and droplets in the charge air flow, leading to incorrect throttle control and torque delivery, as sensors interpret water droplets as additional diluents, resulting in excessive aircharge and potential engine misfires.
Innovation Solution
A method is introduced to adjust the throttle based on a dilution threshold, determined by saturation vapor pressure at the throttle inlet temperature, rather than the total aircharge dilution level, when water droplets are present, ensuring accurate aircharge delivery and torque demand, while also adjusting spark timing to account for total aircharge dilution levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the oxygen sensor is positioned downstream of the charge air cooler to enable EGR measurement, then the sensor can detect oxygen concentration changes due to EGR addition, but water droplets from condensate are incorrectly interpreted as EGR, resulting in overestimation of EGR
Solution Approach 1:
A dilution threshold based on saturation vapor pressure acts as an intermediary reference to distinguish between water vapor dilution and EGR dilution. The controller compares the measured oxygen concentration against this threshold to determine whether the observed dilution is due to water droplets or actual EGR, thereby preventing false EGR measurements and ensuring accurate throttle control
Solution Approach 2:
The system changes the parameter used for throttle control from the raw total dilution measurement to a corrected EGR rate calculation. When the measured dilution exceeds the saturation vapor pressure threshold, the controller adjusts the calculation to account for water vapor contribution, effectively changing how the dilution parameter is interpreted to maintain measurement precision while ensuring reliability
2Quantity of substance
If the throttle is adjusted based on total aircharge dilution level including water droplets, then the dilution level increases, but this results in overestimation of required aircharge and incorrect throttle control
Solution Approach 1:
The controller applies partial correction to the dilution measurement by using the dilution threshold to identify and exclude the water vapor portion of total dilution. Rather than discarding the entire measurement, it selectively accounts for water vapor contribution when the threshold is exceeded, applying the appropriate level of correction to maintain accurate throttle control
Solution Approach 2:
The system implements feedback control by continuously monitoring the oxygen sensor output, comparing it against the dilution threshold, and adjusting the throttle position based on the corrected EGR rate. This closed-loop feedback ensures that throttle control remains accurate even when water droplets are present in the aircharge
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 prevents overestimation of EGR, ensuring precise throttle control and torque delivery, reducing the risk of engine misfires and maintaining efficiency by differentiating between EGR and water droplets in the aircharge dilution.
Implementation Method 1
an oxygen sensor, which may be employed during non-EGR conditions to determine the oxygen content of fresh intake air
Implementation Method 2
during certain operating conditions such as increased charge airflow, condensate formed within the CAC may be released as water droplets into the charge airflow
Implementation Method 3
A dilution threshold may be based on a saturation vapor pressure at a throttle inlet temperature
Data Source
AI summary
Methods and systems are provided for adjusting a throttle based on an intake oxygen sensor output. In one example, a method may include adjusting a position of a throttle based on a dilution threshold and a total aircharge dilution level, the total dilution aircharge level based on an output of an intake oxygen sensor. Additionally, spark timing may be adjusted based on the total aircharge dilution level.