Three Way Catalyst Oxygen Purge Control via Inflection Point Detection
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Solution Overview
Problem
The performance of three way catalysts deteriorates as they degrade, making it difficult to control oxygen storage capacity (OSC) and resulting in reduced exhaust gas purification efficiency, especially during the cold engine period when the OSC variation is large and sensitive.
Innovation Solution
Determining an inflection point in the OSC variation during the cold engine period and controlling the oxygen purge period differently around this point, by increasing the purge period linearly before the inflection point and setting a predetermined value after it, using a controller that measures OSC and heat load with temperature and exhaust gas flow rate detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxygen purge period is kept fixed, then the control system is simple, but the catalyst performance deteriorates as the three way catalyst degrades and OSC variation increases
Solution Approach 1:
The oxygen purge period is changed from a fixed value to a dynamic value that varies based on the measured OSC. The controller adjusts the purge period according to the relationship between OSC and heat load, allowing the system to adapt to catalyst degradation and maintain optimal performance throughout the catalyst's service life.
Solution Approach 2:
The control system monitors the OSC parameter and uses it to determine the appropriate oxygen purge period. By changing the purge period parameter based on measured OSC values and pre-stored relationships, the system optimizes catalyst performance without requiring complex real-time calculations.
2Productivity
If the oxygen purge period is extended to consume stored oxygen, then the purification rate of nitrogen oxide improves, but the catalyst performance deteriorates due to excessive fuel injection
Solution Approach 1:
The oxygen purge period is dynamically adjusted based on the measured OSC and pre-stored relationships between OSC, heat load, and optimal purge periods. This ensures that fuel is injected only to the extent necessary to consume stored oxygen, avoiding excessive fuel consumption while maintaining high nitrogen oxide purification rates.
3Quantity of substance
If the three way catalyst is controlled in a region where OSC is below a certain value, then the oxygen storage capacity is sufficient, but control becomes difficult due to large variation of catalyst performance
Solution Approach 1:
The system continuously measures the OSC and uses this feedback to determine the appropriate oxygen purge period. By monitoring OSC variations and comparing them against pre-stored relationships, the controller can maintain the catalyst in an optimal operating region and adjust control strategies based on real-time catalyst state, making control easier even as the catalyst degrades.
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 optimal control of three way catalyst performance and improved exhaust gas purification by adjusting the oxygen purge period based on the OSC variation, maintaining catalyst efficiency and reducing emissions.
Implementation Method 1
In a fuel cut state, unburned air passes through the three way catalyst so that oxygen is stored in the three way catalyst
Implementation Method 2
an oxygen purge (O2 purge) function which excessively injects fuel at the time of reinjecting the fuel to consume oxygen
Implementation Method 3
a three way catalyst converter in which a noble metal is immersed is disposed in an exhaust system of the vehicle to accelerate the oxidation of hydrocarbon, oxidation of carbon monoxide
Implementation Method 4
a three way catalyst converter in which a noble metal is immersed is disposed in an exhaust system of the vehicle to accelerate the oxidation of hydrocarbon, oxidation of carbon monoxide, and reduction of nitrogen oxide
Data Source
AI summary
A method for controlling an exhaust gas purification apparatus as a catalyst oxygen purge control method during a cold engine period of an exhaust gas purification apparatus including a three way catalyst (TWC) converter purifying exhaust gas exhausted from the engine includes determining whether a fuel cut condition of an injector which injects the fuel to the combustion chamber is satisfied; performing a fuel cut of the injector when the fuel cut condition is satisfied; determining heat load of the three way catalyst by use of a temperature detector and an exhaust gas flow rate detector; measuring oxygen storage capacity (OSC) stored in the three way catalyst according to the heat load; determining an inflection point by use of variation amount of the OSC; and controlling oxygen purge period differently around the inflection point.