Low-Pressure EGR Control Using Oxygen Sensor Compensation
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Solution Overview
Problem
Existing methods for determining the mass flow rate of a low-pressure exhaust gas recirculation (EGR) circuit in internal combustion engines suffer from poor precision and reliability due to the interference of hydrocarbons in the exhaust gases, affecting the accuracy of oxygen measurement by UEGO linear oxygen sensors.
Innovation Solution
A method that uses a combination of sensors and compensation factors to improve the estimation of the EGR circuit's incidence by accounting for oxygen and hydrocarbon presence, involving the use of UEGO sensors along the intake and exhaust pipes, and air flow meters to calculate the mass flow rates and oxygen percentages, ensuring accurate oxygen measurement and compensation for unburned hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UEGO linear oxygen sensor is used to measure oxygen percentage in the intake pipe, then the EGR incidence can be determined, but the measurement precision deteriorates when exhaust gases with rich air/fuel equivalence ratio are recirculated due to hydrocarbon interference
Solution Approach 1:
The patent introduces a compensation factor as an intermediary element that mediates between the raw oxygen sensor signal and the final EGR incidence calculation. This compensation factor accounts for hydrocarbon interference by being determined as a function of engine operating parameters (load, speed, intake temperature, intake pressure) and is applied to correct the oxygen percentage measurement before calculating EGR incidence, thus resolving the measurement precision deterioration caused by hydrocarbon interference
Solution Approach 2:
The patent changes the parameters used for EGR calculation from direct oxygen measurement alone to a corrected approach that incorporates multiple parameters: engine load, engine speed, intake temperature, intake pressure, and the compensation factor. This multi-parameter approach allows the system to adapt to varying operating conditions and compensate for hydrocarbon interference dynamically, maintaining measurement precision across different engine states
2Measurement precision
If a mass flow rate sensor is provided along the bypass pipe to detect EGR mass flow rate, then the EGR incidence can be determined, but the reliability deteriorates over time
Solution Approach 1:
The patent extracts the problematic mass flow rate sensor from the EGR circuit and replaces it with a calculation-based approach. Instead of directly measuring EGR mass flow rate with a physical sensor that degrades over time, the system calculates EGR incidence by combining oxygen sensor data with compensation based on engine operating parameters, thereby eliminating the reliability issues associated with long-term sensor operation in the harsh EGR environment
Solution Approach 2:
The patent replaces the mechanical/physical mass flow rate sensor with a computational system that uses electrical signals from the oxygen sensor and processing of engine parameters. This substitution of a physical measurement device with a calculation-based system eliminates the reliability problems of sensors degrading in the hot, chemically active EGR environment while maintaining the ability to determine EGR incidence accurately
3Ease of operation
If the UEGO sensor measures oxygen in the presence of unburned hydrocarbons, then the EGR incidence estimation can be performed, but the measurement precision deteriorates due to simultaneous detection of oxygen and hydrocarbons
Solution Approach 1:
The patent converts the harmful effect of hydrocarbon presence into a beneficial compensation mechanism. Rather than treating hydrocarbon interference as a problem to be eliminated, the system uses the known relationship between engine operating parameters and hydrocarbon content to calculate a compensation factor. This factor is applied to correct the oxygen measurement, transforming the interference into an opportunity for improved accuracy through systematic compensation
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 enhances the precision and reliability of EGR circuit control, providing a more accurate estimation of the EGR incidence, which is crucial for optimal engine combustion and performance.
Implementation Method 1
a sensor (30) arranged along said intake pipe (6) and designed to determine a percentage (O2) of oxygen contained in a volume of the gas mixture flowing through said intake pipe (6)
Data Source
Figure 1
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AI summary
A method to determine the mass flow rate of a low-pressure exhaust gas recirculation EGR circuit (EGRLP) of an internal combustion engine (1) comprising a first linear sensor (30) to measure the quantity of oxygen available in the mixture of fresh air taken in and exhaust gases flowing through the intake pipe (6) and a second linear sensor (25) to measure the quantity of oxygen available in the flow of exhaust gases; the method comprises the steps of determining the air/fuel equivalence ratio (λ) of the exhaust gases by means of the second sensor (25); in case the exhaust air/fuel equivalence ratio is rich, calculating the percentage (O2real) of total oxygen contained in the mixture flowing through the intake pipe (6) as a function of the air/fuel equivalence ratio (λ) of the exhaust gases determined by means of the second sensor (25) and of the percentage (O2) of oxygen determined by means of the first sensor (30).