EGR Pressure Sensor Diagnostics Using MAP Comparison
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Solution Overview
Problem
Existing EGR systems face challenges in accurately estimating EGR flow rates due to sensor degradation and EGR cooler plugging, leading to inaccurate EGR valve adjustments and potential engine dilution, which affects fuel efficiency and emissions quality.
Innovation Solution
A method using two pressure sensors positioned upstream and downstream of the EGR valve to estimate EGR flow rates and diagnose sensor degradation by comparing current pressure readings with pre-calibrated plots, eliminating the need for an orifice and allowing for rationalization of the EGR pressure sensor offset during valve closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a differential pressure sensor is used to estimate EGR flow rate across a fixed orifice, then EGR flow can be measured, but the orifice causes restriction in EGR flow decreasing maximum possible flow
Solution Approach 1:
The patent removes the fixed orifice from the EGR passage, extracting the flow restriction element that was causing the contradiction. Instead of measuring pressure drop across an orifice, the system uses pressure sensors upstream and downstream of the EGR valve to estimate flow without physical restriction.
Solution Approach 2:
The patent introduces an intermediary calculation method using the relationship between manifold air pressure (MAP) and EGR pressure (EGRP) to estimate EGR flow rate. This intermediary approach allows flow estimation without direct differential pressure measurement across a restrictive orifice.
2Ease of operation
If EGR flow rate is estimated using a pressure sensor, then EGR valve opening can be adjusted, but sensor degradation leads to inaccurate measurement and undesired engine dilution
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the relationship between MAP and EGRP, compares it against pre-calibrated curves, and detects sensor degradation. This feedback loop maintains reliable EGR control even as sensors age by identifying when they deviate from expected performance characteristics.
Solution Approach 2:
The patent performs preliminary calibration during engine operation to establish the relationship between MAP and EGRP for different EGR valve openings. This pre-calibration data is stored and used as a reference to detect future sensor degradation, allowing the system to anticipate and correct for sensor drift before it causes problems.
3Temperature
If an EGR cooler is housed in the EGR passage to cool EGR, then combustion chamber temperatures are reduced, but contaminants deposit in the cooler plugging it and affecting EGR flow
Solution Approach 1:
The patent performs preliminary calibration of the MAP-EGRP relationship under various operating conditions, including different EGR flow rates and temperatures. This pre-calibration captures the system's behavior before cooler plugging occurs, providing a baseline for detecting degradation and allowing the system to compensate for reduced flow capacity.
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 improves the accuracy of EGR flow rate estimation, reduces the risk of engine dilution, and enhances fuel efficiency and emissions quality by detecting sensor degradation and cooler plugging, ensuring robust EGR system operation.
Implementation Method 1
EGR flow rate through an EGR passage may be estimated as a function of a pressure drop across the EGR valve
Implementation Method 2
EGR effectively cools combustion chamber temperatures thereby reducing NOx formation
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 may include comparing a current relationship between an output of the EGR pressure sensor and a manifold air pressure (MAP) and a pre-calibrated relation between the output of the EGR pressure sensor and the MAP to detect degradation of the EGR pressure sensor.