Exhaust Purification System Oxygen Storage Control
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Solution Overview
Problem
In internal combustion engines, after the oxygen storage amount of the catalyst reaches a certain threshold, the target air-fuel ratio is set to a rich ratio to deplete oxygen, leading to the emission of unburned gases like HC and CO, causing deterioration in exhaust emission.
Innovation Solution
An exhaust purification system with an ammonia detection device and air-fuel ratio control that adjusts the air-fuel ratio to decrease oxygen storage in the catalyst, and an abnormality judgment system to detect issues if the ammonia detection device output does not rise to a reference value, using voltage control to manage the air-fuel ratio and prevent excessive unburned gas emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the target air-fuel ratio is set to a rich ratio after oxygen storage reaches threshold, then the oxygen storage amount of the catalyst decreases, but unburned gas (HC, CO) emissions increase causing deterioration of exhaust emission
Solution Approach 1:
The system uses feedback control by monitoring the output of the ammonia detection device and adjusting the air-fuel ratio accordingly. When the ammonia detection device output exceeds a threshold, the system switches to rich control to reduce oxygen storage, but simultaneously monitors that the ammonia output rises appropriately to prevent excessive unburned gas emission. This closed-loop feedback mechanism resolves the contradiction by dynamically balancing oxygen storage reduction with emission control.
Solution Approach 2:
The system changes the air-fuel ratio parameter dynamically based on catalyst oxygen storage conditions. By adjusting the air-fuel ratio from stoichiometric to rich conditions in response to oxygen storage threshold, the system controls the chemical composition of exhaust gas to manage both oxygen depletion and unburned gas emission, resolving the technical contradiction through parameter optimization.
2Quantity of substance
If rich control is maintained until ammonia detection device output rises to reference value, then oxygen storage is reduced, but unburned gas emission deteriorates before ammonia output reaches threshold
Solution Approach 1:
The abnormality judgment part provides feedback monitoring to ensure the ammonia detection device responds appropriately to rich control. By verifying that ammonia output rises to the reference value within expected parameters, the system ensures reliable operation and prevents prolonged rich control that would cause unburned gas emission deterioration, thus maintaining emission quality while reducing oxygen storage.
3Measurement precision
If the voltage applied to downstream side air-fuel ratio sensor is controlled to precisely detect air-fuel ratio, then detection precision improves, but system complexity increases
Solution Approach 1:
The system adjusts the voltage parameter applied to the downstream side air-fuel ratio sensor based on operating conditions. By dynamically changing the sensor voltage to optimize detection precision for different air-fuel ratio ranges, the system achieves high measurement accuracy without requiring a completely complex detection system, as it uses parameter optimization rather than structural complexity.
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 system effectively suppresses the deterioration of exhaust emission by ensuring the air-fuel ratio is maintained within optimal limits, reducing unburned gas and NOX emissions, and preventing oxygen depletion in the catalyst.
Implementation Method 1
an air-fuel ratio control part configured to control an air-fuel ratio of inflowing exhaust gas flowing into the catalyst; and an abnormality judgment part configured to judge abnormality of the ammonia detection device, wherein the air-fuel ratio control part is configured to perform rich control making the air-fuel ratio of the inflowing exhaust gas richer than a stoichiometric air-fuel ratio so that an oxygen storage amount of the catalyst decreases
Implementation Method 2
an ammonia detection device arranged in an exhaust passage of an internal combustion engine at a downstream side of a catalyst in a direction of flow of exhaust
Implementation Method 3
an air-fuel ratio detection device arranged in the exhaust passage at the downstream side of the catalyst in the direction of flow of exhaust
Data Source
AI summary
An exhaust purification system of an internal combustion engine comprises a catalyst 20, an air-fuel ratio sensor 41, a current detection device 61, a voltage application device 60, a voltage control part 71 and an air-fuel ratio control part 72. The air-fuel ratio control part controls the air-fuel ratio so that the output current of the air-fuel ratio sensor becomes a predetermined target value. The voltage control part performs at least one of voltage lowering control setting the applied voltage to a first voltage lower when the air-fuel ratio becomes higher than a lean judged air-fuel ratio, and a voltage raising control setting the applied voltage to a second voltage when the air-fuel ratio becomes lower than a rich judged air-fuel ratio. The reference voltage is a voltage at which the output current of the air-fuel ratio sensor becomes zero when the air-fuel ratio is the stoichiometric air-fuel ratio.