Three-Way Catalyst Diagnosis Using Flow-Based Oxygen Capacity
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Solution Overview
Problem
Conventional methods for diagnosing three-way catalyst deterioration in internal combustion engines fail to account for the impact of gas flow amount, leading to erroneous judgments due to changes in substantial oxygen storage capacity.
Innovation Solution
Set the reference oxygen storage capacity based on the gas flow amount, specifically using intake air amount, to offset the decrease in substantial oxygen storage capacity caused by increased gas flow speed, thereby preventing erroneous deterioration diagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reference oxygen storage capacity is used for catalyst deterioration diagnosis, then the diagnosis method is simple, but erroneous judgment occurs when gas flow amount changes
Solution Approach 1:
The reference oxygen storage capacity is changed from a fixed value to a dynamic value that varies according to the gas flow amount. The ECU dynamically adjusts the reference value based on detected gas flow conditions, allowing the diagnosis system to adapt to different operating conditions and eliminate erroneous judgments caused by flow rate variations.
Solution Approach 2:
The reference oxygen storage capacity parameter is modified based on the gas flow amount parameter. By establishing a relationship between these two parameters, the system adjusts the reference value to compensate for the effects of varying gas flow rates on oxygen storage capacity measurements, thereby improving diagnosis accuracy.
2Device complexity
If gas flow amount is not considered in oxygen storage capacity measurement, then the measurement process is simple, but substantial oxygen storage capacity decreases due to increased gas flow speed
Solution Approach 1:
The system implements a feedback mechanism where the gas flow amount is continuously detected and used to adjust the reference oxygen storage capacity. This feedback loop ensures that the reference value always reflects the current operating conditions, maintaining reliable measurements across varying flow rates without requiring complex measurement procedures.
3Measurement precision
If reference oxygen storage capacity is adjusted according to gas flow amount, then deterioration diagnosis accuracy is improved, but the control system becomes more complex
Solution Approach 1:
The ECU uses its existing sensing capabilities to detect gas flow amount and automatically adjusts the reference oxygen storage capacity without requiring external intervention or additional complex hardware. The system serves itself by utilizing available data and computational resources to perform the adjustment, minimizing the increase in overall system 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
Accurately diagnose catalyst deterioration by adjusting the reference oxygen storage capacity according to gas flow conditions, reducing false positives and maintaining effective catalyst performance.
Implementation Method 1
the catalyst ability to occlude and release oxygen, i.e. the so-called oxygen storage capability
Data Source
AI summary
An internal combustion engine (1) has a three-way catalyst (15). An engine controller (9) has an oxygen amount calculation unit (102) determining an amount of oxygen flowing into the three-way catalyst (15) per unit time and an oxygen storage amount calculation unit (108) estimating a current oxygen storage amount by integrating positive and negative oxygen amount. A reference oxygen storage capacity calculation unit (107) outputs a reference oxygen storage capacity according to an intake air amount output by an intake air amount calculation unit (101) so that as the intake air amount is larger, the reference oxygen storage capacity becomes smaller. A catalyst diagnosis unit (104) judges catalyst deterioration by comparing a current oxygen storage capacity with the reference oxygen storage capacity set by taking the intake air amount into consideration.