Exhaust Catalyst Light-Off Detection via NOx Sensor
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Solution Overview
Problem
Current methods for determining the start of conversion in exhaust gas catalytic converters are indirect, slow, and inaccurate, making it difficult to assess the condition and efficiency of the converter, which is crucial for optimizing heating and reducing pollutant emissions.
Innovation Solution
A method using a NOx sensor downstream of the catalytic converter to measure NOx concentration changes, allowing for direct and precise determination of the light-off temperature and converter state, eliminating the need for oxygen storage capacity-based indirect methods, and enabling assessments of aging and poisoning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect determination using oxygen storage capacity (OSC) with lambda sensors is used, then the light-off determination can be performed, but the determination is slow and inaccurate
Solution Approach 1:
The patent replaces the indirect chemical-based OSC measurement method with a direct optical detection method using a light detector. The light detector measures light absorption changes in the exhaust gas stream, which directly indicate NOx conversion status. This substitution provides both faster response time and higher measurement precision compared to the previous lambda sensor-based OSC method.
2Reliability
If precise determination of light-off is achieved, then the condition assessment and control optimization become possible, but the measurement system becomes more complex
Solution Approach 1:
The patent introduces a light detector as an intermediary device that measures light absorption properties of the exhaust gas. This intermediary provides reliable catalyst condition assessment by detecting changes in light absorption that correlate with NOx conversion efficiency, without requiring complex multi-sensor systems or sophisticated measurement architectures.
3Measurement precision
If direct NOx conversion measurement is implemented, then the measurement precision and speed improve, but the device complexity increases due to additional sensors
Solution Approach 1:
The patent extracts and measures only the relevant optical property (light absorption) that directly indicates NOx conversion status. By focusing on this single key parameter through the light detector, the system achieves high measurement precision without implementing complex multi-parameter sensor systems. The approach extracts the essential information needed from the exhaust gas stream.
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 precise and timely determination of the converter's functionality and condition, allowing for optimized heating and regeneration measures, reducing pollutant emissions and extending converter lifespan.
Implementation Method 1
downstream of the exhaust gas catalytic converter is a NOx sensor (4), which extends into the exhaust line, wherein the exhaust gas (6) flows around the NOx sensor (4)
Implementation Method 2
exhaust gas purification is achieved in the usual way via a three-way catalyst, as well as additional catalysts upstream and downstream of the three-way catalyst
Data Source
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AI summary
The invention relates to a method for performing on-board diagnostics of an exhaust catalyst in the exhaust aftertreatment system of an internal combustion engine of a vehicle. The exhaust aftertreatment system comprises the exhaust catalyst and at least one NOx sensor arranged downstream of the exhaust catalyst. First, after the internal combustion engine is started, during which the exhaust catalyst has a temperature below its light-off temperature, the onset of the initial conversion of nitrogen oxides is determined by measuring the NOx concentration in the exhaust gas with the NOx sensor. Subsequently, a parameter is determined that characterizes the start of this initial conversion. The determined parameter is compared with an expected value of this parameter, and the state of the exhaust catalyst is determined based on this comparison.