Engine EGR Valve Mode Selection for NOx and Deposit Control
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Solution Overview
Problem
Existing engine systems with EGR devices face increased NOx emissions when EGR cut is performed unnecessarily due to low deposit risk on the EGR valve, leading to inefficient recirculation of exhaust gas.
Innovation Solution
An engine with an EGR device that includes an EGR valve controlled by a control unit to select from multiple modes based on engine speed and fuel injection amount, allowing the EGR valve to be opened maximally in the third mode to reduce NOx emissions while minimizing deposit accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EGR cut is performed based on deposit adhesion amount estimation value being equal to or greater than threshold, then deposit accumulation on EGR valve is prevented, but NOx emission increases when deposit risk is low
Solution Approach 1:
The patent changes the control parameters from a single threshold-based deposit adhesion amount to multiple parameters including engine speed, fuel injection amount, and intake air amount. By evaluating these parameters collectively, the system determines deposit risk more accurately and adjusts EGR valve control accordingly, reducing unnecessary EGR cuts and lowering NOx emissions while maintaining reliable EGR valve operation.
2Reliability
If EGR valve is kept closed to prevent deposit accumulation, then EGR valve reliability is maintained, but NOx emission control performance deteriorates
Solution Approach 1:
The patent implements dynamic EGR valve control by continuously monitoring engine operating conditions (engine speed, fuel injection amount, intake air amount) and adjusting the EGR valve opening degree in real-time. This dynamic approach allows the system to maintain EGR valve reliability by closing the valve only when deposit risk is high, while maximizing NOx emission control efficiency by keeping the valve open when conditions are favorable.
Solution Approach 2:
The system periodically evaluates engine operating parameters to determine whether to maintain EGR valve closure or transition to EGR recirculation, creating a rhythmic control pattern that balances deposit prevention with emission control based on current engine conditions.
3Reliability
If EGR recirculation is stopped to avoid deposit accumulation, then EGR valve reliability is improved, but exhaust gas treatment efficiency decreases
Solution Approach 1:
The patent changes the control strategy from binary (EGR on/off based on deposit threshold) to continuous parameter-based control. By monitoring engine speed, fuel injection amount, and intake air amount, the system dynamically adjusts EGR recirculation to maintain valve reliability while minimizing harmful emissions through optimized exhaust gas treatment.
Data Source
AI summary
An engine includes a control unit that controls the EGR valve. The control unit selects a predetermined control mode from at least a first mode, a second mode, and a third mode according to at least an engine speed and a fuel injection amount, and controls the EGR valve in the selected control mode. The first mode is a control mode in which the EGR valve is fully closed. The second mode is a control mode in which the opening degree of the EGR valve is adjusted according to the operation state of the engine. The third mode is a control mode in which an ON period in which the opening degree of the EGR valve is adjusted according to the operation state of the engine and an OFF period in which the EGR valve is fully closed are repeated.