Oxygen Sensor HC Cross-Sensitivity for Catalyst Efficiency Measurement
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Solution Overview
Problem
Existing methods for determining hydrocarbon-conversion efficiency of catalysts in internal combustion engines are either unreliable, fuel-consuming, or influenced by dynamic effects, and do not accurately measure HC-conversion efficiency independently of operating points.
Innovation Solution
A method using an oxygen-sensitive sensor downstream from the catalyst to detect signals at varying HC fractions, leveraging HC cross-sensitivity to determine HC-conversion efficiency by evaluating differences in sensor signals, which minimizes the influence of oxygen partial pressure and operating fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If late post-injection of fuel is used to artificially increase HC fraction for measuring catalyst temperature, then HC-conversion efficiency measurement is enabled, but fuel consumption and final HC emissions increase
Solution Approach 1:
The patent extracts and utilizes the HC cross-sensitivity property of the oxygen sensor as a separate measurement channel. By evaluating the difference between the sensor signal and the expected oxygen partial pressure, the method obtains HC-conversion efficiency information without requiring additional fuel injection, thus eliminating the energy loss associated with post-injection methods
Solution Approach 2:
The oxygen sensor acts as an intermediary that indirectly measures HC-conversion efficiency through its cross-sensitivity to HC. Instead of directly measuring HC concentration or catalyst temperature, the method uses the sensor's response to oxygen partial pressure changes caused by HC oxidation, providing a fuel-efficient measurement pathway
2Reliability
If oxygen storage capacity (OSC) measurement is used to diagnose catalyst, then diagnostic capability is provided, but the measurement is influenced by dynamic effects and does not directly measure HC-conversion efficiency
Solution Approach 1:
The patent replaces the mechanical/dynamic OSC measurement method with a chemical-based approach. Instead of measuring oxygen storage through lambda probe transitions during rich-lean cycling, the method uses the oxygen sensor's electrochemical response to oxygen partial pressure changes, which directly reflects HC oxidation activity and conversion efficiency
Solution Approach 2:
The method creates a copy of the HC oxidation process signal through the oxygen sensor's cross-sensitivity. By measuring the sensor's response to oxygen consumption during HC oxidation, the system obtains a direct electrical signal representation of HC-conversion efficiency, avoiding the indirect and dynamic OSC measurement approach
3Measurement precision
If HC fraction in exhaust gas is increased to achieve significant temperature increase for measurement, then HC-conversion efficiency can be measured, but emissions of hydrocarbons increase
Solution Approach 1:
The patent converts the harmful effect of HC cross-sensitivity (which was previously a source of measurement error) into a beneficial measurement mechanism. By utilizing the sensor's natural response to HC oxidation through oxygen consumption, the method measures HC-conversion efficiency without requiring elevated HC emissions, turning a diagnostic challenge into a measurement advantage
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 provides a reliable, fuel-efficient, and independent measurement of HC-conversion efficiency, reducing process-related HC emissions and enhancing diagnostic accuracy.
Implementation Method 1
a signal of the downstream sensor which exhibits an HC cross sensitivity is detected in a first situation in which a first HC fraction is present in the exhaust gas upstream from the catalyst
Implementation Method 2
exhaust gas catalysts that oxidize the hydrocarbons in the presence of oxygen in order to form carbon dioxide and water
Implementation Method 3
owing to the exothermic characteristics of the HC combustion that takes place in the catalyst
Data Source
AI summary
The invention relates to a method to determine the HC-conversion efficiency of a catalyst, which is situated in the exhaust gas flow path of an internal combustion engine and which is configured to convert hydrocarbons, by means of an oxygen-sensitive sensor that is installed downstream from the catalyst in the exhaust gas flow path and that exhibits a cross sensitivity to hydrocarbons. The method comprises: detecting a first signal of the downstream sensor in a first situation in which a first HC fraction is present in the exhaust gas upstream from the catalyst; detecting a second signal of the downstream sensor in a second situation in which a second HC fraction that is higher than the first HC fraction is present in the exhaust gas upstream from the catalyst; and determining the HC-conversion efficiency of the catalyst as a function of the first and second signals of the downstream sensor.