Exhaust Gas Catalyst Error Detection via Dual Sensor Quality Values
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Solution Overview
Problem
Existing internal combustion engine systems face challenges in accurately monitoring and reducing nitrogen oxide (NOx) emissions, particularly in distinguishing between mixture component errors and catalytic converter issues, while maintaining efficient pollutant conversion and adhering to stringent emission regulations.
Innovation Solution
A method and device that utilize two exhaust gas probes for lambda and trim control, determining HC and NOx quality values to assess oxygen storage capacity and NOx emissions, and adjust controller parameters to stabilize emissions, thereby reducing NOx emissions and avoiding unnecessary repairs or capacity impairment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing monitoring methods are used to assess catalytic converter status, then the system can detect converter degradation, but it cannot reliably distinguish between mixture component errors and catalytic converter errors
Solution Approach 1:
The patent segments the error detection process into two distinct evaluation paths: one for mixture component errors and one for catalytic converter errors. By dividing the diagnostic approach and using separate quality value assessments (lambda quality value and NOx quality value), the system can identify which specific component is malfunctioning rather than treating all errors uniformly.
Solution Approach 2:
The patent introduces new diagnostic parameters (HC quality value, NOx quality value, lambda quality value) that change based on the operational state of different system components. By monitoring how these parameters change under forced stimulation conditions, the system can distinguish between mixture component issues and catalytic converter issues through their distinct parameter response patterns.
2Measurement precision
If additional sensors are installed to improve emission monitoring accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing second exhaust gas probe (lambda probe downstream of the catalytic converter) multi-functional by using it for both traditional trim control and new diagnostic purposes (determining HC quality value and NOx quality value). This allows the single sensor to serve multiple functions including emission monitoring, converter status assessment, and error source identification without adding additional hardware.
Solution Approach 2:
The system uses its existing sensor infrastructure and control mechanisms to perform self-diagnosis. The lambda probe downstream of the catalytic converter is already present for trim control, and the patent enables this existing sensor to additionally monitor converter status and distinguish error sources through intelligent signal evaluation, making the system self-sufficient for comprehensive monitoring.
3Reliability
If forced stimulation is applied to monitor catalytic converter oxygen storage capacity, then converter status can be assessed, but the signal amplitude from downstream probes becomes too small to reliably detect emissions
Solution Approach 1:
The patent applies forced stimulation excessively (stronger than normally required for trim control) specifically for diagnostic purposes. By using a richer air/fuel mixture during forced stimulation, the system creates larger fluctuations in the downstream probe signal that can be reliably detected and evaluated, even though this exceeds normal operational stimulation levels.
Solution Approach 2:
The patent implements periodic forced stimulation cycles interspersed with normal operation. During these periodic diagnostic phases, the system temporarily applies enriched mixture conditions to generate detectable signal fluctuations for converter assessment, then returns to normal trim control operation, allowing both functions to coexist without continuous interference.
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 allows for reliable identification and reduction of NOx emissions, distinguishing between mixture component and catalytic converter errors without additional sensors, ensuring efficient pollutant conversion and emission stabilization, thus optimizing engine operation and reducing the risk of drive capacity impairment.
Implementation Method 1
when the oxygen storage unit is emptied, oxidation is assisted and stored oxygen molecules are prevented from deactivating sub-regions of the exhaust gas catalytic converter
Implementation Method 2
When oxygen is introduced into the oxygen storage unit, nitrogen oxides in particular are reduced
Implementation Method 3
Three-way catalytic converters are deployed as exhaust gas catalytic converters in petrol combustion engines in particular
Implementation Method 4
An actual value of the air/fuel ratio is determined as a function of the signal from a linear lambda probe upstream of the exhaust gas catalytic converter
Data Source
AI summary
An internal combustion engine has an exhaust gas catalyst, a first exhaust gas sensor that is arranged for use in lambda control, and a second sensor that is arranged for trim control. The measuring signal of the second sensor is used to determine a NOx quality value depending on the HC quality value and the NOx correction factor. A lambda quality value is determined depending on an actual value and a basic set value of the air/fuel ratio. An error indicator is determined depending on the lambda quality value and the NOx quality value, the error indicator being representative of a mixture component error in a first range and being representative of an exhaust gas catalyst error in a second range. At least one control parameter of a trim control and/or the trim set value of the trim control is adapted depending on the NOx correction factor.