High-Pressure EGR Valve Diagnosis via Recirculation Amount Difference
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Solution Overview
Problem
The reliability of failure diagnosis for high-pressure EGR valves is low due to varying pressure conditions caused by exhaust gas pulsation, making it difficult to accurately determine the actual recirculation amount, whereas low-pressure EGR valves have higher reliability due to more stable intake conditions.
Innovation Solution
An exhaust gas recirculation control device that includes a valve control system with detectors for total intake gas, fresh air, and pressure differences, allowing for comparative analysis of actual and target recirculation amounts across both low-pressure and high-pressure EGR passages to improve the reliability of high-pressure EGR valve diagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the actual high-pressure recirculation amount is calculated based on pressure difference and valve opening, then the measurement can be obtained, but the reliability of failure diagnosis is low due to exhaust gas pulsation causing inaccurate pressure difference measurement
Solution Approach 1:
The patent introduces a mediator (the relationship between total recirculation amount, low-pressure recirculation amount, and high-pressure recirculation amount) to indirectly determine the high-pressure recirculation amount. Instead of directly measuring the unreliable pressure difference, the system calculates high-pressure recirculation amount as the difference between total recirculation amount (from intake gas measurement) and low-pressure recirculation amount (from reliable low-pressure path measurement), thereby avoiding direct measurement of the pulsating pressure difference while still obtaining the required information for failure diagnosis
2Reliability
If the actual low-pressure recirculation amount is calculated by subtracting fresh air amount from total intake gas amount, then the failure diagnosis reliability is high due to stable intake conditions, but this method cannot directly diagnose high-pressure EGR valve status
Solution Approach 1:
The patent segments the total recirculation amount measurement into two independent measurement paths: low-pressure path (using stable intake conditions for reliable baseline measurement) and high-pressure path (using the same stable intake conditions combined with pressure difference). By segmenting the diagnosis into low-pressure EGR valve diagnosis (using total intake gas minus fresh air) and high-pressure EGR valve diagnosis (using total intake gas minus low-pressure recirculation), the system achieves both high reliability through the stable intake measurement and comprehensive adaptability by covering both valve types
Data Source
AI summary
An exhaust gas recirculation control device of an engine includes an exhaust turbocharger having a turbine disposed in an exhaust passage and a compressor disposed in an intake passage, low-pressure and high-pressure EGR passages connecting the exhaust passage downstream of the turbine to the intake passage upstream of the compressor and connecting the exhaust passage upstream of the turbine with the intake passage downstream of the compressor, respectively, low-pressure and high-pressure EGR valves disposed in the low-pressure and high-pressure EGR passages and for changing cross-sectional areas thereof, respectively, a valve control device for controlling openings of the low-pressure and high-pressure EGR valves, a total intake gas amount detector for detecting a total intake gas amount, a fresh air amount detector for detecting a fresh air amount, and a pressure difference detector for detecting a pressure difference between the exhaust and intake passage sides of the high-pressure EGR valve.