EGR Flow Detection via MAP-MAF Strategy and Intrusive Valve Closure
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Solution Overview
Problem
Existing EGR systems face challenges in accurately measuring excessive EGR flow, particularly in Differential Pressure Over Valve (DPOV) systems without a Differential Pressure Feedback (DPFE) sensor, leading to potential inaccuracies due to MAF sensor drift, which can result in false excessive EGR flow indications and non-compliance with emissions standards.
Innovation Solution
A method is introduced that uses a MAP-MAF strategy to estimate EGR flow rate based on the difference between manifold absolute pressure and mass airflow sensors, and performs an intrusive test by commanding the EGR valve to a closed position to confirm excessive flow, utilizing both DPOV and MAP-MAF estimates to set a diagnostic code only when both methods consistently indicate an excessive flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DPFE sensor is used to measure EGR flow, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the EGR flow measurement function from the DPFE sensor and implements it using existing sensors (MAP and MAF sensors) that are already part of the engine management system. This eliminates the need for the additional DPFE sensor while maintaining measurement capability through calculation based on pressure and airflow data.
Solution Approach 2:
The patent makes the existing MAP and MAF sensors perform the additional function of EGR flow measurement. These sensors already serve other engine control functions, and the patent extends their utility to also provide EGR flow data through computational processing, thereby avoiding additional hardware.
2Measurement precision
If MAF sensor drift is not compensated, then device complexity remains low, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the EGR flow calculation continuously monitors the relationship between MAP and MAF sensor readings. When drift is detected through inconsistent EGR flow measurements over time, the system adjusts or compensates for the drift by comparing against expected EGR flow values and correcting the sensor data accordingly.
Solution Approach 2:
The patent performs preliminary drift compensation by establishing baseline relationships between MAP, MAF, and EGR flow under known operating conditions. This pre-calibration data is stored and used to correct for sensor drift during normal operation, preventing measurement errors before they affect EGR control.
3Reliability
If intrusive testing is performed to confirm excessive EGR flow, then diagnostic reliability is improved, but productivity decreases
Solution Approach 1:
The patent implements periodic intrusive testing where the EGR valve is temporarily closed for a brief period to confirm excessive flow conditions. This periodic action is performed at scheduled intervals rather than continuously, allowing normal EGR operation to resume while still providing diagnostic confirmation when needed.
Solution Approach 2:
The patent applies partial intrusive testing by closing the EGR valve for only a portion of the diagnostic cycle rather than continuously. This partial action is sufficient to confirm the presence of excessive flow (by observing the change in sensor readings when EGR is blocked) while minimizing impact on overall system productivity.
Data Source
AI summary
Methods and systems are provided for diagnostics of exhaust gas recirculation (EGR) components including an EGR pressure sensor. In one example, a method for an exhaust gas recirculation (EGR) system of a vehicle comprises diagnosing an excessive EGR flow rate via an MAP-MAF strategy, the MAP-MAF strategy including estimating an EGR flow rate based on a difference between an output of a manifold absolute pressure (MAP) sensor of the vehicle and an output of a mass airflow (MAF) sensor of the vehicle; and in response to stable intrusive conditions being met, intrusively commanding an EGR valve of the EGR system to a closed position to confirm the diagnosed excessive EGR flow rate. If the excessive flow is detected after the EGR valve is commanded to the closed position, a diagnostic code may be set.