Diagnosing Exhaust Gas Systems Using Lean-Rich Lambda Transitions
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Solution Overview
Problem
Current methods for diagnosing exhaust gas systems of internal combustion engines are inefficient, leading to additional fuel consumption and worsened emission values, as they require testing under various operating conditions, including rich and lean mixtures, which is not independent of the operating point.
Innovation Solution
A method that switches an internal combustion engine from a lean to a rich operation to test the functional operability of catalytic converters and lambda sensors, using a binary lambda sensor to classify their performance based on Nernst voltage changes, thereby eliminating the need for additional fuel consumption during diagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional operating conditions with rich and lean mixtures are used to test the exhaust gas system, then the diagnostic completeness is improved, but the fuel consumption increases and emission values worsen
Solution Approach 1:
The patent performs a thrust operation (clearing out the three-way catalytic converter) before the actual diagnosis. This preliminary action prepares the system by ensuring the three-way catalytic converter is cleared, which allows the subsequent diagnosis of the four-way catalytic converter and binary lambda sensor to be performed using only the exhaust gases already present during normal operation, without requiring additional rich/lean cycling
Solution Approach 2:
The patent uses the exhaust gases produced during normal engine operation to perform the diagnosis. The binary lambda sensor and four-way catalytic converter are tested using the exhaust stream that naturally occurs during the clearing out operation, eliminating the need for separate test operations with additional fuel consumption
2Reliability
If additional operating conditions with rich and lean mixtures are used to test the exhaust gas system, then the diagnostic completeness is improved, but the emission values worsen
Solution Approach 1:
The thrust operation that clears the three-way catalytic converter is performed before diagnosis. This preliminary action ensures the converter is properly cleared, allowing the subsequent diagnosis to proceed during normal operation without requiring additional rich/lean cycles that would generate extra emissions
Solution Approach 2:
The diagnosis utilizes the exhaust gases already present during the clearing operation and normal engine operation. By using the self-generated exhaust stream rather than introducing additional rich/lean test conditions, the system achieves diagnostic completeness without generating additional harmful emissions
3Reliability
If the diagnosis is performed independently of the operating point, then the diagnostic reliability is improved, but the fuel consumption and emissions increase
Solution Approach 1:
The patent performs a clearing out operation of the three-way catalytic converter before the actual diagnosis. This preliminary action creates optimal conditions for diagnosis by ensuring the three-way converter is cleared, which allows the four-way catalytic converter and binary lambda sensor to be tested during normal operation rather than requiring independent operating point tests
Solution Approach 2:
The patent combines the clearing out function and the diagnostic function into a single operational sequence. The thrust operation serves dual purposes: it clears the three-way catalytic converter and simultaneously provides the conditions necessary for diagnosing the four-way catalytic converter and binary lambda sensor, eliminating the need for separate test operations
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 efficient diagnosis of catalytic converters and lambda sensors without additional fuel use, improving fuel efficiency and emission control by determining the state of the catalytic converters and lambda sensors through changes in exhaust gas values and measurement values during the transition from lean to rich operations.
Implementation Method 1
a test of the functional operability of the at least one binary lambda sensor and/or of at least one four-way catalytic converter is performed on the basis of a lambda change when the internal combustion engine is switched from a lean operation to a rich operation
Implementation Method 2
exhaust gases are generated which must be subsequently treated by means of an exhaust gas system in order to make the operation of the internal combustion engine compliant with environmental regulations, such as for examples the regulations for exhaust gas limits
Data Source
AI summary
The present invention relates to a method for diagnosing an exhaust gas system of an internal combustion engine with at least one three-way catalytic converter, at least one four-way catalytic converter and at least one binary lambda sensor, wherein during the testing of the functional operability of the at least one binary lambda sensor and/or of at least one four-way catalytic converter on the basis of a lambda change with a changeover of the internal combustion engine from a lean operation to a rich operation following a thrust operation clearing out at least one three-way catalytic converter occurs.