EGR Rate Estimation in Internal Combustion Engines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In internal combustion engines with low pressure EGR systems, the long passage distance between EGR gas introduction and the combustion chamber leads to reduced estimation accuracy of EGR rate during transient engine operation, causing unstable combustion and deteriorated fuel consumption.
Innovation Solution
A control device that uses detection signals from EGR sensors downstream of the throttle valve, air flow sensors, and EGR valve opening degree sensors to estimate EGR rates, with delay processing and learning correction to improve accuracy, ensuring appropriate EGR gas introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the EGR rate is estimated using only EGR valve opening degree and differential pressure, then the device complexity is reduced, but the measurement precision deteriorates during transient engine operation
Solution Approach 1:
The patent combines multiple estimation methods by merging the physical model-based estimation (using valve opening and pressure) with EGR sensor-based detection. The control device integrates both approaches and uses their difference to correct estimation errors, thereby improving measurement precision without excessively increasing device complexity.
Solution Approach 2:
The patent implements feedback control by continuously comparing the EGR rate estimated from the physical model with the EGR rate detected by the EGR sensor. The difference between these values is used to correct the physical model parameters, creating a closed-loop system that improves estimation accuracy during transient operation.
2Measurement precision
If an EGR sensor is provided in the intake pipe to detect EGR rate, then the measurement precision improves in constant operation region, but the response speed deteriorates during transient state
Solution Approach 1:
The patent performs preliminary estimation of the EGR rate using the physical model (which responds quickly to changes) before the EGR sensor can provide accurate measurement. This preliminary estimate is then corrected using the sensor data, allowing the system to maintain fast response while achieving high precision.
Solution Approach 2:
The patent introduces a correction mechanism as an intermediary between the slow EGR sensor and the control system. The correction value, derived from the difference between sensor detection and physical model estimation, mediates to accelerate the overall response while maintaining the precision benefits of the sensor.
3Loss of time
If the passage distance between EGR gas introduction and combustion chamber is reduced, then the response time improves, but the device complexity increases due to system redesign
Solution Approach 1:
The patent replaces the need for mechanical system redesign (shortening passage distance) with a control-based solution. By using advanced estimation algorithms that compensate for the long passage delay, the system achieves fast response characteristics without physically modifying the intake system configuration.
Solution Approach 2:
The patent changes the parameters used for EGR rate estimation to account for the long passage distance. By using a physical model that incorporates the specific characteristics of the low pressure EGR system and correcting it with sensor data, the system maintains accuracy despite the extended gas transit time.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A novel control device for an internal combustion engine capable of highly accurately estimating an EGR amount (rate) during the transient state is provided. A first EGR rate is determined using, as an input, a detection signal of an EGR sensor (9, 25) provided on the downstream side of a throttle valve (7) which adjusts the flow rate of a mixed gas of air and EGR gas flowing through an intake pipe (10), a second EGR rate is estimated by calculating a predetermined equation using, as an input, at least a detection signal of an air flow sensor (3) and an EGR valve opening degree sensor, a third EGR rate is determined by carrying out delay processing on the second EGR rate corresponding to a response delay of the EGR sensor, and the second EGR rate is subjected to learning correction by reflecting a difference between the third EGR rate and the first EGR rate.