Engine Control System Oxygen Storage Management
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Solution Overview
Problem
Existing internal combustion engine control systems fail to maintain high exhaust purification catalyst oxygen storage capacity and prevent NOx and unburned gas emissions, as they often switch air-fuel ratios prematurely, leading to reduced purification performance and increased emissions.
Innovation Solution
A control system that alternates air-fuel ratios to lean and rich settings based on oxygen storage levels, with increased lean and rich degrees during steady engine operation, and adjusts switching reference storage amounts based on cumulative exhaust gas and time conditions to optimize oxygen storage and emission control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the target air-fuel ratio is switched from lean to rich before the oxygen storage amount reaches maximum, then NOx emissions are reduced, but the oxygen storage capacity of the exhaust purification catalyst deteriorates over time
Solution Approach 1:
The control system periodically alternates the target air-fuel ratio between lean and rich conditions. When the oxygen storage amount reaches a predetermined reference value (before maximum capacity), the system switches to rich air-fuel ratio to release stored oxygen, then returns to lean condition to recharge oxygen storage. This periodic cycling maintains the catalyst's oxygen storage capacity while preventing NOx emissions by ensuring oxygen is available for NOx reduction reactions.
Solution Approach 2:
The control system uses feedback from the downstream air-fuel ratio sensor and oxygen storage amount calculations to dynamically adjust the target air-fuel ratio. When the oxygen storage amount approaches the reference value, the system detects this condition and switches to rich condition to release oxygen, then monitors when oxygen storage is sufficient to switch back to lean condition. This closed-loop feedback ensures optimal balance between emission control and catalyst performance maintenance.
2Reliability
If the oxygen storage capacity is maintained high through frequent switching, then purification performance is improved, but unburned gas and NOx emissions increase
Solution Approach 1:
The control system changes the air-fuel ratio parameter dynamically based on oxygen storage conditions. By adjusting the timing of switches between lean and rich conditions based on the oxygen storage amount reaching a predetermined reference value, the system optimizes the balance between maintaining purification performance and controlling emissions. The reference value is set to ensure sufficient oxygen storage for effective purification while preventing excessive switching that would increase emissions.
3Reliability
If the air-fuel ratio is maintained at lean condition for extended periods, then oxygen storage capacity is maintained, but NOx flows out from the exhaust purification catalyst
Solution Approach 1:
The system implements periodic switching between lean and rich air-fuel ratios based on oxygen storage monitoring. When oxygen storage reaches the predetermined reference value, the system switches to rich condition to release stored oxygen and prevent NOx emissions, then returns to lean condition to recharge oxygen storage. This periodic action ensures that the catalyst maintains sufficient oxygen for purification while preventing NOx breakthrough by releasing oxygen before it becomes depleted.
Data Source
AI summary
A control system of an internal combustion engine which can suppress a drop in the purification performance of an exhaust purification catalyst is provided. The control system of an internal combustion engine is provided with an exhaust purification catalyst and downstream side air-fuel ratio sensor, performs feedback control so that an air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst becomes a target air-fuel ratio, and performs target air-fuel ratio setting control which alternately switches the target air-fuel ratio to a lean set air-fuel ratio which is leaner than a stoichiometric air-fuel ratio and a rich set air-fuel ratio which is richer than the stoichiometric air-fuel ratio. In the control system, when an engine operating state is a steady operating state, compared with when it is not a steady operating state, at least one of a rich degree of the rich set air-fuel ratio or a lean degree of the lean set air-fuel ratio is made to increase.