Engine EGR Control During Catalyst Neutralization After Fuel Cut
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Solution Overview
Problem
The three-way catalyst in internal combustion engines experiences reduced NOx purification capability due to oxygen concentration fluctuations during fuel cuts, leading to potential engine stalls when catalyst neutralization processing is initiated at delayed timings.
Innovation Solution
An internal-combustion-engine control apparatus that includes an exhaust gas recirculation processor and a catalyst neutralization processor, which adjusts exhaust gas recirculation and fuel injection to manage oxygen concentration, preventing engine stalls by anticipating oxygen concentration changes during fuel cuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalyst neutralization processing is executed after fuel injection is resumed following a fuel cut, then the oxygen concentration in the catalyst is reduced and NOx purification capability is restored, but the oxygen concentration may drop too low causing engine stall
Solution Approach 1:
The control device detects oxygen concentration trends before catalyst neutralization processing is fully executed, and preliminarily adjusts the EGR valve to reduce exhaust gas recirculation amount. This preliminary action prevents excessive oxygen concentration drop that would cause engine stall, while still allowing the neutralization processing to restore NOx purification capability.
Solution Approach 2:
The control device continuously monitors oxygen concentration from the oxygen sensor and uses this feedback to dynamically adjust EGR valve operation. When oxygen concentration is detected to be increasing after fuel injection resumes, the system feedback-controls the EGR valve to reduce recirculation, preventing harmful oxygen depletion while maintaining effective catalyst neutralization.
2Productivity
If exhaust gas recirculation is maintained at normal levels during catalyst neutralization processing, then fuel economy is improved, but oxygen concentration drops causing engine stall
Solution Approach 1:
The control device dynamically adjusts the EGR valve operation amount based on real-time oxygen concentration detection. Instead of maintaining a fixed EGR rate, the system varies the recirculation amount according to oxygen concentration trends, allowing high EGR rates (good fuel economy) when oxygen is sufficient, and reducing EGR when oxygen concentration increases after fuel injection resumes.
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 stabilizes oxygen concentration in the catalyst, preventing engine stalls and maintaining efficient NOx purification by anticipating and correcting exhaust gas recirculation amounts based on oxygen sensor readings.
Implementation Method 1
the three-way catalyst increases in internal oxygen concentration... the three-way catalyst is supplied with an excess fuel by setting an air-fuel ratio (A/F) of the exhaust gas to a rich A/F, to thereby oxidize oxygen stored in the three-way catalyst
Implementation Method 2
an oxygen sensor configured to detect an oxygen concentration on a downstream side of the catalyst
Implementation Method 3
an exhaust gas recirculator configured to circulate a part of exhaust gas into the intake passage
Implementation Method 4
the three-way catalyst is supplied with an excess fuel by setting an air-fuel ratio (A/F) of the exhaust gas to a rich A/F, to thereby oxidize oxygen stored in the three-way catalyst
Data Source
AI summary
An internal-combustion-engine control apparatus configured to control an internal combustion engine includes an exhaust gas recirculation processor and a catalyst neutralization processor. The exhaust gas recirculation processor is configured to control an exhaust gas recirculator, based on an operating state of the internal combustion engine. The catalyst neutralization processor is configured to: determine whether an oxygen concentration detected by an oxygen sensor is greater than or equal to a predetermined first threshold; and execute, when the oxygen concentration detected by the oxygen sensor is greater than or equal to the predetermined first threshold, catalyst neutralization processing in which fuel injection into the internal combustion engine is executed in a fuel-rich atmosphere having a richer air-fuel ratio than a stoichiometric air-fuel ratio to thereby consume at least a part of oxygen stored in a catalyst.