Exhaust Gas Sensor Diagnosis Using Recirculation Overrun
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for diagnosing exhaust gas catalytic converters, such as SCR catalytic converters, are costly and lack diagnostic robustness due to the need for multiple sensors and reliance on mathematical models, which can be inaccurate.
Innovation Solution
A method using a single exhaust gas sensor upstream from the catalytic converter, combined with an exhaust gas recirculation system, measures exhaust gas component concentrations during different engine operation modes to determine the catalytic converter's status, eliminating the need for additional sensors and mathematical models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple exhaust gas sensors are installed upstream and downstream from the catalytic converter to measure concentration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary substance (balloon or flexible membrane) that transmits pressure changes from the exhaust gas space to the sensor. This allows the sensor to indirectly measure exhaust gas component concentration through pressure variations caused by catalytic conversion, eliminating the need for direct placement of multiple sensors in the exhaust stream.
Solution Approach 2:
The patent replaces the mechanical/conventional approach of using multiple exhaust gas sensors directly in the exhaust stream with an indirect measurement system using pressure sensing and an intermediary transmission mechanism. This substitution reduces sensor quantity while maintaining measurement capability.
2Device complexity
If mathematical models are used to determine raw emissions concentration, then device complexity is reduced, but measurement precision and diagnostic robustness deteriorate
Solution Approach 1:
The system uses the catalytic converter's own operation to generate measurable effects. The conversion of exhaust gas components by the catalytic converter creates pressure changes that can be detected and used to assess converter status, making the system self-diagnostic without requiring external complex measurement or modeling systems.
Solution Approach 2:
The patent implements a feedback mechanism where the pressure changes detected during catalytic conversion are used to assess the converter's status and performance. This closed-loop approach allows continuous monitoring and diagnosis based on real-time pressure variations caused by the converter's own operation.
3Measurement precision
If exhaust gas is recirculated during overrun mode to measure concentration, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent employs periodic action by utilizing the engine's overrun mode (a periodic operating condition) to enable concentration measurement. The measurement is performed during specific time windows when the engine is in overrun mode, allowing accurate measurement without requiring continuous disruption of normal operation.
Solution Approach 2:
The system adapts to dynamic engine operating conditions by utilizing the transient overrun mode to perform measurements. The diagnosis system dynamically adjusts measurement timing based on engine state, capturing pressure changes during the specific dynamic condition when exhaust gas recirculation occurs.
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 cost-effective and reliable diagnosis of the catalytic converter's efficiency and reductant metering, ensuring precise NOx conversion without the uncertainties of multiple sensors or models, enhancing diagnostic robustness.
Implementation Method 1
the exhaust gas tract has an exhaust gas recirculation system that is designed so that at least some of the exhaust gas can be removed from an exhaust gas pipe of the exhaust gas tract downstream from the exhaust gas catalytic converter and can be fed to the internal combustion engine
Implementation Method 2
measuring a first concentration of the exhaust gas component upstream from the exhaust gas catalytic converter by means of the exhaust gas sensor
Implementation Method 3
a exhaust gas catalytic converter that is arranged in an exhaust gas pipe of the internal combustion engine of a motor vehicle and that is suitable for the conversion of at least one exhaust gas component
Data Source
AI summary
The invention relates to a method and to a motor vehicle for diagnosing an exhaust gas catalytic converter (28), which is arranged in an exhaust gas tract (20) of an internal combustion engine (12) and is suitable for converting at least one exhaust gas component, wherein the exhaust gas tract (20) has an exhaust gas sensor (48) arranged upstream of the exhaust gas catalytic converter (28) and has an exhaust gas recirculation system (38), which is designed to remove at least part of the exhaust gas from an exhaust gas duct (24) of the exhaust gas tract (20) downstream of the exhaust gas catalytic converter (28) and to feed the removed exhaust gas to the internal combustion engine (12). The method comprises the following steps: measuring a first concentration (NOX1) of the exhaust gas component upstream of the exhaust gas catalytic converter (28) by means of the exhaust gas sensor (48) during fueled operation of the internal combustion engine (12), recirculating at least part of the exhaust gas by means of the exhaust gas recirculation system (38) during unfueled overrun of the internal combustion engine (12), measuring a second concentration (NOX2) of the exhaust gas component by means of the exhaust gas sensor (48) during the unfueled overrun of the internal combustion engine (12), and determining a state of the exhaust gas catalytic converter (28) in dependence on the first and second concentrations (NOX1, NOX2) of the exhaust gas component.