EGR Valve Step Motor Control for Combustion Deterioration
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Solution Overview
Problem
Existing engine systems face challenges in quickly resolving abnormalities in the exhaust gas recirculation (EGR) valve during engine deceleration, leading to potential combustion deterioration and drivability issues due to delayed opening of the EGR valve and excessive or insufficient gas flow.
Innovation Solution
An engine system with an EGR valve controlled by a step motor, where an operating-state detecting unit diagnoses abnormalities and controls the valve to hold at a first opening degree smaller than necessary before deceleration, then rapidly opening to a second degree to resolve issues, thereby shortening the time to achieve the necessary opening and prevent combustion deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the EGR valve is controlled to open rapidly to resolve abnormalities during engine deceleration, then the time to achieve necessary opening degree is reduced, but combustion deterioration may occur due to excessive EGR gas flow
Solution Approach 1:
The EGR valve is opened in advance before the abnormality actually occurs during engine deceleration. The control unit predicts the timing of abnormality based on engine operating conditions and pre-opens the EGR valve to a first opening degree, ensuring the valve is ready to prevent combustion deterioration when the abnormality occurs, while avoiding excessive gas flow that would cause combustion issues.
Solution Approach 2:
The EGR valve opening degree is dynamically adjusted through multiple stages: first opened to a first opening degree in advance, then adjusted to a second opening degree when abnormality is detected, and finally adjusted to a third opening degree based on real-time engine conditions. This dynamic control prevents both combustion deterioration and excessive gas flow by adapting the valve position to the actual operating state.
2Reliability
If the EGR valve is held at a closed position during engine deceleration, then EGR gas leakage is prevented, but abnormalities such as foreign matter lodging cannot be resolved quickly
Solution Approach 1:
The EGR valve is pre-opened to a first opening degree before abnormality occurs during engine deceleration. This preliminary action ensures the valve is in a state ready to quickly resolve abnormalities (such as foreign matter lodging) when they occur, while the controlled opening degree prevents excessive EGR gas flow that would cause combustion deterioration.
Solution Approach 2:
The EGR valve opening degree is dynamically adjusted: first opened to a first opening degree in advance, then adjusted to a second opening degree when abnormality is detected to quickly resolve the issue, and finally adjusted to a third opening degree based on real-time engine conditions. This dynamic control balances the need to quickly resolve abnormalities with the need to prevent excessive gas flow.
3Measurement precision
If the step motor of the EGR valve is controlled precisely to maintain target opening degree, then EGR flow rate accuracy is improved, but step-out errors cause divergence between target and actual opening degree
Solution Approach 1:
The control unit monitors the actual opening degree of the EGR valve and compares it with the target opening degree. When step-out or foreign matter lodging is detected (indicated by abnormal intake pressure), the control unit adjusts the valve opening degree accordingly. This feedback mechanism ensures accurate EGR flow rate control despite step motor imperfections.
Solution Approach 2:
The EGR valve is opened in advance before abnormality occurs. By pre-positioning the valve at a first opening degree, the system proactively compensates for potential step-out errors and ensures the valve is ready to maintain accurate EGR flow control when abnormalities occur during engine deceleration.
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 configuration enhances the operational performance of resolving EGR valve abnormalities by quickly opening the valve to the required degree, minimizing combustion deterioration and improving drivability by reducing EGR gas leakage and avoiding excessive gas flow.
Implementation Method 1
a step motor configured to drive the valve element
Data Source
AI summary
An engine system includes an injector, an EGR device (including an EGR valve having a step motor) to recirculate part of exhaust gas of an engine as EGR gas to the engine, and an electronic control unit (ECU) to control the injector, the EGR valve, and others based on an operating state of the engine. The ECU is configured to diagnose foreign-matter lodging abnormality of the EGR valve and a lodged foreign-matter diameter based on detected intake pressure during engine deceleration. When existence of the abnormality and the foreign-matter diameter are determined, the ECU controls the step motor to hold the EGR valve at a first opening degree smaller than a second opening degree needed to remove a foreign matter before fuel cut to the engine by the injector.