Upstream Oxygen Sensor Calibration Using Downstream Feedback
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Solution Overview
Problem
Existing methods for determining air-fuel ratios in internal combustion engines are biased by aromatic hydrocarbons, particularly under cold engine conditions, and do not account for power-train variabilities and fuel differences among vehicles.
Innovation Solution
An engine exhaust system method adjusts the sensor calibration correction value of an upstream exhaust sensor based on a downstream sensor reading, under steady-state conditions with the engine temperature below a threshold and active catalyst, to correct for biases caused by aromatic hydrocarbons, ensuring accurate air-fuel ratio determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional lambda offset method is used to account for aromatic hydrocarbons, then air-fuel ratio determination can be adjusted based on estimated aromatic hydrocarbon amounts, but measurement precision deteriorates under cold engine conditions and does not account for vehicle-specific variations
Solution Approach 1:
The system uses feedback from the downstream oxygen sensor to continuously adjust and refine the sensor calibration correction value. The downstream sensor reading serves as feedback to verify and update the correction applied to the upstream sensor, enabling the system to adapt to vehicle-specific variations and improve measurement precision over time through learned calibration values
Solution Approach 2:
The system changes the calibration parameters of the upstream oxygen sensor based on downstream sensor feedback. By adjusting the sensor calibration correction value derived from downstream readings, the system adapts to different vehicle configurations, fuel types, and operating conditions, resolving the contradiction between measurement precision and adaptability
2Productivity
If upstream oxygen sensor is used for air-fuel ratio determination, then real-time control is achieved, but measurement precision deteriorates due to bias from aromatic hydrocarbons in cold engine conditions
Solution Approach 1:
The downstream oxygen sensor acts as an intermediary to validate and correct the upstream sensor readings. By comparing upstream readings with downstream readings (which are not affected by aromatic hydrocarbon bias), the system can identify and correct biases in real-time, maintaining both real-time control capability and measurement precision
Solution Approach 2:
The system replaces reliance on a single upstream mechanical sensor with a dual-sensor electronic feedback system. Instead of depending solely on the upstream sensor that is susceptible to bias, the system uses electronic processing of downstream sensor data to correct upstream readings, substituting electronic correction for mechanical sensor limitations
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 fuel economy and reduces emissions by providing accurate air-fuel ratio readings even under cold engine conditions, accounting for vehicle-specific variations.
Implementation Method 1
If the catalyst is active, the hydrocarbons present in the exhaust stream will be oxidized in the catalyst
Data Source
AI summary
Methods and system for controlling air-fuel ratios in an internal combustion engine are disclosed. One embodiment comprises, adjusting a sensor calibration correction value of an exhaust sensor upstream of a catalyst based on an exhaust sensor downstream of the catalyst. The adjustment of the sensor calibration correction value takes advantage of the fact that certain aromatic hydrocarbons causing errors in the reading of the upstream sensor are not present at the downstream sensor due to sufficient catalytic activity of a catalyst positioned between the sensors.