EGR Control Strategy for Engine Output and Stability
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Solution Overview
Problem
Conventional engine control devices using exhaust gas recirculation (EGR) face challenges in maintaining engine output and combustion stability in high load ranges, where increased EGR gas amounts lead to unstable combustion and torque fluctuations.
Innovation Solution
An engine control device with an EGR system that includes a turbocharger, EGR valve, and EGR cooler, where the EGR rate is controlled to be lower in high load regions to prevent output decrease and stability deterioration, while being higher in low load regions to reduce pumping loss and improve fuel efficiency, and the ignition timing is adjusted to prevent knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the EGR gas amount is increased as the engine load increases in the high rotation and high load range, then the engine temperature is reduced and knocking is suppressed, but the engine output decreases and combustion stability deteriorates
Solution Approach 1:
The patent changes the EGR rate parameter based on engine operating conditions. Specifically, it sets the EGR rate to be lower than a predetermined threshold value when the engine operates in the high rotation and high load range, while allowing higher EGR rates in other operating ranges. This dynamic parameter adjustment resolves the contradiction by preventing excessive EGR gas introduction that would cause output loss while still utilizing EGR for knock suppression when appropriate.
Solution Approach 2:
The patent implements dynamic control of the EGR valve opening degree based on real-time engine operating conditions (rotation speed and load). The EGR rate is continuously adjusted according to the engine's current state, transitioning from static to dynamic control. This allows the system to optimize the balance between knock suppression and output maintenance by adapting the EGR gas amount to specific operating scenarios.
2Temperature
If the EGR gas amount is increased as the engine load increases in the high rotation and high load range, then the engine temperature is reduced and heat damage is suppressed, but combustion stability deteriorates and torque fluctuation occurs
Solution Approach 1:
The patent adjusts the EGR rate parameter dynamically based on engine operating conditions. By setting the EGR rate below a predetermined threshold in the high rotation and high load range where combustion stability is critical, the system prevents excessive EGR gas from destabilizing combustion while still achieving temperature control benefits in other operating ranges where higher EGR rates are permissible.
Solution Approach 2:
The patent applies different EGR rate strategies to different operating conditions. Instead of using a uniform EGR rate across all engine operations, it implements localized control where the EGR rate is specifically limited in the high rotation and high load range, while allowing more aggressive EGR in other ranges. This localized quality approach optimizes combustion stability where needed while maintaining temperature control benefits elsewhere.
3Loss of energy
If the EGR rate is increased to reduce pumping loss and improve fuel efficiency, then fuel efficiency is improved, but engine output decreases and combustion stability deteriorates in high load ranges
Solution Approach 1:
The patent implements conditional parameter adjustment where the EGR rate is set below a predetermined threshold specifically in the high rotation and high load range, while allowing higher EGR rates in other operating conditions. This resolves the contradiction by preventing output loss during high load operations while still utilizing EGR for pumping loss reduction and fuel efficiency improvement in appropriate operating ranges.
Solution Approach 2:
The patent employs dynamic EGR rate adjustment based on real-time engine operating conditions. The EGR valve opening degree is continuously modified according to the engine's rotation speed and load, transitioning from static to adaptive control. This dynamic approach allows the system to capture fuel efficiency benefits through EGR in suitable conditions while preventing output degradation in high load scenarios.
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
The solution effectively suppresses engine output decrease and combustion stability deterioration in high load ranges, enhances fuel efficiency, and reduces knocking by optimizing EGR gas introduction and ignition timing, while ensuring stable operation across varying load conditions.
Implementation Method 1
an EGR cooler that cools the EGR gas passing through the EGR passage
Implementation Method 2
a turbocharger including a compressor provided on an intake passage and a turbine provided on an exhaust passage
Implementation Method 3
a compressor provided on an intake passage
Data Source
AI summary
An engine control device including: a turbocharger; an EGR device that includes an EGR passage, an EGR valve, and an EGR cooler; and a PCM that, based on an operation state of an engine, controls the EGR valve to adjust an EGR rate that is a ratio of an EGR gas amount to a total amount of gas introduced to a cylinder of the engine. The PCM controls the EGR valve such that, in a high load range and a medium load range for the engine, the EGR device recirculates the EGR gas into an intake passage; and controls the EGR valve such that an EGR rate in the high load range is lower than an EGR rate in the medium load range at a same engine speed.