EGR Valve Control for Accurate Ratio Estimation
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Solution Overview
Problem
In low-pressure loop EGR systems, the differential pressure generating valve cannot set its opening to an extremely small value, leading to a discrepancy between the target and actual EGR ratios, especially during deceleration, which affects engine control and fuel efficiency.
Innovation Solution
A method is introduced to estimate the actual EGR ratio by calculating a provisional EGR ratio and correcting it based on the differential pressure across the EGR valve, ensuring accurate engine control even when the target EGR ratio is small.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the degree of opening of the differential pressure generating valve is set to an extremely small value to achieve a high target EGR ratio, then the EGR ratio control is improved, but the amount of air supplied to the cylinder deteriorates
Solution Approach 1:
The patent changes the control parameter from valve opening degree to differential pressure. By controlling the differential pressure across the EGR valve rather than directly controlling the valve opening, the system can achieve the desired EGR ratio without requiring the differential pressure generating valve to be closed to an extremely small opening, thus maintaining adequate air supply to the cylinder.
2Measurement precision
If the differential pressure generating valve maintains a small degree of opening to generate negative pressure for EGR, then the EGR ratio is improved, but the actual EGR ratio deviates from the target EGR ratio when the required negative pressure cannot be generated
Solution Approach 1:
The patent implements feedback control by measuring the actual differential pressure across the EGR valve and using this information to adjust the EGR valve opening. The control unit calculates the actual EGR ratio based on the measured differential pressure and compares it with the target EGR ratio, then adjusts the EGR valve to minimize the difference, ensuring reliable engine control even when the differential pressure generating valve cannot generate the required negative pressure.
3Quantity of substance
If the differential pressure generating valve is fully opened to ensure adequate air supply, then the air supply to cylinder is improved, but the ability to generate required negative pressure for small target EGR ratios deteriorates
Solution Approach 1:
The patent introduces the EGR valve as an intermediary component between the differential pressure generating valve and the EGR passage. The EGR valve acts as a fine-adjustment device that can precisely control the EGR gas flow based on the differential pressure conditions, allowing the differential pressure generating valve to maintain a larger opening for adequate air supply while the EGR valve compensates to achieve the target EGR ratio.
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 allows for more accurate estimation of the actual EGR ratio, enabling proper engine control and preventing fuel efficiency deterioration, even under conditions where the differential pressure is insufficient.
Implementation Method 1
The differential pressure generating valve generates a negative pressure by narrowing a degree of opening of the differential pressure generating valve
Data Source
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AI summary
A controller, in shifting the state of the EGR system from the EGR operating state to the EGR non-operating state at the time of performing the deceleration of the vehicle, calculates a provisional EGR ratio that is a provisional value of the current EGR ratio, estimates the provisional EGR ratio as the actual EGR ratio when a fore-and-aft differential pressure of the EGR valve is equal to or more than a predetermined value, performs correction to make the provisional EGR ratio smaller, and estimates the corrected provisional EGR ratio as the actual EGR ratio when the fore-and-aft differential pressure of the EGR valve is less than the predetermined value.