Engine EGR Control System Transient Estimation
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Solution Overview
Problem
Existing engine control systems struggle to accurately estimate the EGR rate and in-cylinder oxygen concentration, especially during transient operations like acceleration and deceleration, and in conditions of engine deterioration, due to limitations in sensor responsiveness and fouling issues.
Innovation Solution
An engine control system that employs an EGR flow sensor for direct detection of EGR gas flow rate, using both hot-wire-based and electromagnetic flow sensors, and switches between two estimation methods based on engine operation states to accurately calculate EGR rate and in-cylinder oxygen concentration, ensuring robustness and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an O2 sensor is used to detect oxygen concentration for estimating in-cylinder oxygen concentration, then the system can provide a detection mechanism, but the detection responsiveness to transient changes is insufficient
Solution Approach 1:
The patent segments the detection task by using multiple sensors (O2 sensor for steady-state oxygen concentration, airflow sensor for air intake measurement) rather than relying on a single sensor. This division allows each sensor to operate in its optimal range, with the O2 sensor providing accurate but slow responses and the airflow sensor providing fast but less direct measurements, which are then combined through calculation to achieve both accuracy and responsiveness.
2Ease of manufacture
If an airflow sensor is disposed at a position spaced away from the combustion chamber to detect intake air amount, then the sensor is easier to install, but the detected amount does not coincide with the actual air taken into the pipe during transient operation
Solution Approach 1:
The patent introduces calculation logic as an intermediary between the airflow sensor measurement and the actual in-cylinder air amount. The ECU calculates the actual intake air amount by combining the airflow sensor output with other parameters (such as throttle opening, engine speed, and temperature) to compensate for the measurement errors introduced by the sensor's remote position and the presence of intermediate components.
3Adaptability or versatility
If the engine operates in transient conditions with engine deterioration and fouling, then the engine can handle varying loads, but the accuracy of EGR rate and in-cylinder oxygen concentration estimation deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the ECU continuously monitors the output of both the O2 sensor and airflow sensor, compares the estimated EGR rate and oxygen concentration with target values, and adjusts the EGR valve opening and fuel injection parameters accordingly. This closed-loop control compensates for measurement errors and maintains accuracy even during transient operation and engine deterioration.
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 precise engine combustion control, maintaining torque stability and reducing exhaust gas fluctuations, while preventing fouling and ensuring long-term sensor durability, even in challenging conditions.
Implementation Method 1
from the viewpoint of the responsiveness and the resistance to fouling, it is desirable that the above-described EGR flow sensor be a hot-wire-based flow sensor
Implementation Method 2
using both hot-wire-based and electromagnetic flow sensors
Data Source
AI summary
An engine that re-circulates its exhaust gas suffers decreased accuracy in estimating an EGR rate real-time especially while the operating state of the engine is in a transitional state, which often results in torque fluctuations and deteriorated exhaust gas.A sensor for directly detecting an EGR flow rate is disposed in an EGR path. An EGR rate and in-cylinder oxygen concentration are calculated from the output value of that sensor. In addition, when this EGR rate calculation method is used, the calculation is properly switched between a steady operation state characterized by a low load and small rotational fluctuations and a transitional operating state including the acceleration and deceleration. This makes it possible to correctly estimate the EGR rate and the in-cylinder oxygen concentration under a wide range of engine operation conditions, and thereby to avoid the fluctuation of torque and the deterioration of exhaust gas.