Diagnosing Lambda Sensor Offsets in Multi-Flow Exhaust Systems
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Solution Overview
Problem
In a multi-flow exhaust gas system of an internal combustion engine, it is challenging to diagnose lambda sensor errors upstream of the catalytic converter due to overlapping errors from multiple banks, leading to undetected exothermic reactions that increase exhaust gas temperature, which complicates temperature modeling and affects emissions.
Innovation Solution
A method is developed to identify and correct opposite lambda offsets by measuring the difference between actual and modeled exhaust gas temperatures, adjusting lambda setpoint values alternately between banks to minimize this difference, allowing for precise diagnosis and correction of individual sensor offsets without damaging the catalytic converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lambda sensors are arranged in multiple exhaust gas banks upstream of the catalytic converter, then emissions control is improved, but diagnosis of individual sensor errors becomes difficult due to overlapping errors compensating each other
Solution Approach 1:
The patent segments the diagnosis process by introducing a temporary isolation mechanism where individual lambda sensors are sequentially disconnected from the control loop. This allows each sensor to be tested independently by comparing its lambda signal against a reference model, thereby resolving the diagnostic ambiguity caused by multiple sensors operating simultaneously in parallel exhaust banks.
Solution Approach 2:
The patent introduces a reference lambda signal generated from a calibrated model as an intermediary standard for comparison. This reference signal serves as a mediator that enables the detection of deviations in individual lambda sensors by providing a known baseline against which each sensor's output can be independently evaluated, even when multiple sensors are operating.
2Productivity
If lambda offset errors are not detected and corrected, then the control system continues operating, but exothermic reactions in the catalytic converter cause overheating and potential damage
Solution Approach 1:
The patent implements preliminary diagnosis and correction of lambda sensor offsets before they can cause harmful exothermic reactions in the catalytic converter. By continuously monitoring lambda signals and comparing them against reference values, the system detects sensor offsets early and applies corrective adjustments to the fuel injection or air intake, preventing the accumulation of errors that would lead to dangerous temperature increases.
Solution Approach 2:
The patent employs a feedback mechanism where the lambda sensor signals are continuously compared against a reference model, and any detected offsets trigger corrective actions. This closed-loop feedback system ensures that lambda offset errors are identified and compensated in real-time, preventing the development of conditions that would cause exothermic reactions and catalytic converter damage while maintaining continuous operation.
3Measurement precision
If lambda sensor diagnosis is performed in multi-flow exhaust systems, then sensor accuracy can be maintained, but the complexity of the diagnostic system increases due to multiple banks and Y junction configurations
Solution Approach 1:
The patent implements a universal diagnostic approach that works across different exhaust system configurations (single-flow, multi-flow, Y junction arrangements) using the same fundamental methodology. The diagnostic system uses a standardized reference model and comparison technique that can be applied to any lambda sensor regardless of its position in the exhaust system, thereby maintaining measurement precision without proportionally increasing system complexity.
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 enables accurate diagnosis and correction of lambda sensor offsets, preventing overheating of the catalytic converter and maintaining optimal emissions control by accounting for individual sensor errors, thus ensuring the longevity of the catalytic converter and maintaining emissions control.
Implementation Method 1
These lean and rich exhaust gas constituents would react exothermically in the exhaust gas catalytic converter which may be, in particular, a three-way catalytic converter. These exothermic reactions heat the exhaust gas catalytic converter and thereby increase the exhaust gas temperature downstream of the exhaust gas catalytic converter.
Data Source
AI summary
A method for diagnosing a plurality of lambda sensors which are arranged upstream of an exhaust gas catalytic converter in a plurality of exhaust gas banks of a multi-flow exhaust gas system of an internal combustion engine. An opposite lambda offset of the lambda sensors is identified (54) when a difference (ΔT) between a measured exhaust gas temperature (Tmeasure) and a modeled exhaust gas temperature (Tmod) downstream of the exhaust gas catalytic converter overshoots a threshold value (S).