Air Flow Meter Diagnosis Using Pre-Diagnosis to Reduce Emissions
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Solution Overview
Problem
Existing diagnostic methods for air flow meters in supercharged internal combustion engines with recirculation circuits are intrusive, leading to increased fuel consumption and pollutant emissions, and are prone to false or non-detections.
Innovation Solution
A method that includes a pre-diagnosis step to assess the air flow meter's accuracy using two thresholds, only proceeding to a main diagnostic step that cuts off exhaust gas recycling if the pre-diagnosis is inconclusive, thereby reducing the need for intrusive adjustments and minimizing engine operation disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the main diagnostic step is performed by cutting off exhaust gas recirculation, then measurement precision of air flow meter is improved, but fuel consumption and pollutant emissions increase
Solution Approach 1:
The patent applies preliminary action by implementing a pre-diagnosis step that compares air flow meter reading with filling model calculation under normal operating conditions (with EGR active). This preliminary assessment identifies obvious faults without requiring the intrusive main diagnostic step, thereby avoiding unnecessary fuel consumption and emissions while still detecting significant flow meter failures.
Solution Approach 2:
The patent uses partial action by implementing a two-stage diagnostic approach. The pre-diagnosis performs a partial assessment using less intrusive means (comparing measurements under normal operation), and only if this partial assessment is inconclusive does the system proceed to the full main diagnostic step with EGR cutoff. This minimizes the frequency and duration of energy-intensive diagnostic operations.
2Measurement precision
If the main diagnostic step is performed by cutting off exhaust gas recirculation, then measurement precision of air flow meter is improved, but pollutant emissions increase
Solution Approach 1:
The pre-diagnosis step serves as a preliminary filter that identifies obvious flow meter faults without requiring the intrusive main diagnostic procedure. By detecting significant discrepancies between air flow meter readings and filling model calculations under normal EGR operation, the system avoids unnecessary main diagnostics that would increase pollutant emissions.
Solution Approach 2:
The two-stage diagnostic system applies partial action by using the less intrusive pre-diagnosis method for routine monitoring. The intrusive main diagnostic step with EGR cutoff is performed only partially and selectively - specifically when the pre-diagnosis yields inconclusive results - thereby minimizing overall pollutant emissions while maintaining diagnostic effectiveness.
3Reliability
If pre-diagnosis with two thresholds is implemented, then false diagnoses are reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the diagnostic function into two distinct stages: pre-diagnosis and main diagnosis. Each stage has its own threshold criteria and decision logic. The pre-diagnosis uses two thresholds (first and second thresholds) to categorize results as fault, no fault, or inconclusive, requiring different subsequent actions. This segmentation improves reliability by reducing false diagnoses while keeping each individual stage relatively simple.
Solution Approach 2:
The diagnostic system employs dynamic threshold evaluation where the system adapts its diagnostic approach based on pre-diagnosis results. When the difference between measured and calculated air flow falls between the two thresholds, the system dynamically decides to perform the main diagnostic step. This dynamic adaptation improves diagnostic reliability while managing complexity through conditional logic rather than static rigid structures.
Data Source
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AI summary
The invention relates to a method for diagnosing an air flow meter in a turbocharged internal combustion engine with at least partial low-pressure exhaust gas recirculation. The primary diagnostic of the air flow meter consists of disabling all partial recirculation and comparing the meter reading with an air flow value calculated using a cylinder filling model of the engine. According to the invention, to reduce the frequency of this diagnostic, which leads to increased nitrogen oxide emissions, at least one preliminary diagnostic is performed first, without impacting engine operation, and the primary diagnostic is carried out only if there is uncertainty about the result of this preliminary diagnostic.