Exhaust Purification Catalyst Sulfur Desorption Control
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Solution Overview
Problem
The exhaust purification system of internal combustion engines faces challenges in maintaining catalyst precious metal activity and oxygen storage ability due to sulfur content adsorption, leading to reduced efficiency in removing unburned HC, CO, and NOx, especially at low catalyst temperatures.
Innovation Solution
An exhaust purification system with a control device that alternates the average air-fuel ratio between rich and lean settings and performs inter-cylinder air-fuel ratio control to manage sulfur content desorption, optimizing catalyst operation by adjusting air-fuel ratios based on catalyst temperature to prevent sulfur deposition and maintain oxygen storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the average air-fuel ratio is controlled to be lean to reduce sulfur content adsorption, then the drop in catalyst precious metal activity is suppressed, but the opportunities for sulfur desorption are reduced
Solution Approach 1:
The control device periodically switches the average air-fuel ratio between rich and lean settings in alternating cycles. During lean phases, sulfur adsorption is minimized protecting catalyst activity. During rich phases, sulfur desorption is promoted. This periodic switching resolves the contradiction by providing both protection and regeneration opportunities over time.
Solution Approach 2:
The system dynamically changes the air-fuel ratio parameter between rich and lean states based on catalyst temperature and sulfur loading conditions. By adjusting this critical parameter alternately, the system achieves both sulfur desorption (when rich) and prevention of further adsorption (when lean), resolving the contradiction between maintaining activity and providing desorption opportunities.
2Productivity
If the average air-fuel ratio is controlled to be rich to cause sulfur desorption, then sulfur desorption opportunities are increased, but the drop in oxygen storage ability is accelerated
Solution Approach 1:
The system uses periodic alternating control between rich and lean air-fuel ratios. During rich phases, sulfur desorption is promoted. During lean phases, oxygen storage ability is maintained and recovered. This periodic switching prevents continuous degradation while providing regular desorption opportunities.
Solution Approach 2:
The control device ensures continuous catalyst operation by alternating between rich and lean phases, maintaining useful action throughout. The lean phases compensate for any degradation from rich phases, ensuring continuous oxygen storage ability and catalytic performance while periodically providing sulfur desorption opportunities.
3Reliability
If inter-cylinder air-fuel ratio control is performed to maintain oxygen storage ability, then the oxygen storage ability is maintained, but the complexity of air-fuel ratio control increases
Solution Approach 1:
The control system segments the engine operation into individual cylinder control and average air-fuel ratio control. By controlling air-fuel ratios at the cylinder level and then averaging them, the system maintains oxygen storage ability while managing complexity through structured organization of control parameters.
Solution Approach 2:
The control device performs multiple functions: it controls average air-fuel ratio, performs inter-cylinder air-fuel ratio control, manages sulfur desorption, and maintains oxygen storage ability. By integrating these functions into a single control system, the patent reduces overall complexity while achieving multiple objectives simultaneously.
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 effectively suppresses the drop in catalyst precious metal activity and oxygen storage ability, enhancing the system's ability to remove unburned HC, CO, and NOx by increasing sulfur desorption opportunities and maintaining catalyst efficiency across varying temperatures.
Implementation Method 1
the catalyst precious metal which is carried on the carrier of the exhaust purification catalyst under certain conditions and covers the surface of the catalyst precious metal
Implementation Method 2
exhaust gas which is discharged from a combustion chamber contains sulfur content. Such sulfur content is adsorbed or stored on the surface of the catalyst precious metal
Implementation Method 3
the ability to remove unburned HC, CO, NOx, etc. in the exhaust gas which flows into the exhaust purification catalyst
Data Source
AI summary
An exhaust purification system of an internal combustion engine which has a plurality of cylinders is comprised of an exhaust purification catalyst, a downstream side air-fuel ratio sensor, and a control device which controls the average air-fuel ratio of the exhaust gas and the combustion air-fuel ratios of the cylinders. The control device performs average air-fuel ratio control where it alternately controls the average air-fuel ratio between the rich air-fuel ratio and the lean air-fuel ratio and inter-cylinder air-fuel ratio control where it controls the combustion air-fuel ratios of the cylinders so that the combustion air-fuel ratio becomes the rich air-fuel ratio at least at one cylinder among the plurality of cylinders. In average air-fuel ratio control, the average air-fuel ratio is controlled so that the lean shift amount becomes smaller than the rich shift amount when the temperature of the exhaust purification catalyst is low and the average air-fuel ratio is controlled so that the lean shift amount becomes larger than the rich shift amount when the temperature is high.