Flexible-Fuel Catalyst Diagnosis Using Downstream O2 Signal Reversals
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Solution Overview
Problem
Existing catalyst deterioration diagnostic devices for engines using flexible fuels, which mix gasoline and alcohol, face inaccuracies in diagnosing catalyst deterioration due to variations in fuel properties, leading to erroneous diagnoses and missed detections of catalyst deterioration.
Innovation Solution
A catalyst deterioration diagnostic device that utilizes upstream and downstream oxygen sensors to control the flexible fuel supply based on their signals, adjusting the cycle and amplitude of fuel amount changes to accurately diagnose catalyst deterioration irrespective of fuel mixture ratios, by ensuring the downstream sensor's signal patterns reflect catalyst health accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alcohol-mixed fuel is used in the engine, then the oxygen storage capacity measurement value increases, but the catalyst deterioration diagnosis accuracy deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the fuel injection amount based on the detected alcohol concentration. When alcohol concentration is high, the fuel injection amount is increased to compensate for the lower stoichiometric air-fuel ratio of alcohol (9.0) compared to gasoline (14.6). This ensures that the exhaust gas composition remains optimal for catalyst operation despite using alcohol-mixed fuel, thereby maintaining accurate catalyst deterioration diagnosis while accounting for the increased oxygen storage capacity measurement values
Solution Approach 2:
The patent implements feedback control by continuously monitoring the oxygen concentration in exhaust gas using an air-fuel ratio sensor and adjusting the fuel injection amount accordingly. The system detects the oxygen concentration, compares it to the target gasoline stoichiometry, and modifies the fuel injection to maintain proper exhaust gas composition. This feedback mechanism compensates for the effects of alcohol fuel on oxygen storage capacity measurements, preserving diagnosis accuracy
2Reliability
If the fuel injection amount is increased for alcohol fuel, then the stoichiometric air-fuel ratio control is maintained, but the oxygen storage capacity measurement value changes
Solution Approach 1:
The patent changes the fuel injection amount parameter in response to alcohol fuel detection. Since alcohol has a lower stoichiometric air-fuel ratio (9.0) compared to gasoline (14.6), the system increases the fuel injection amount when alcohol concentration is detected. This parameter adjustment maintains proper stoichiometric control while accounting for the resulting changes in oxygen storage capacity measurement values, allowing the system to distinguish between measurement variations caused by fuel type versus actual catalyst deterioration
3Measurement precision
If the air-fuel ratio is controlled to gasoline stoichiometry with alcohol fuel, then the oxygen concentration detection is maintained, but the catalyst surface reaction efficiency decreases
Solution Approach 1:
The patent uses feedback control through the air-fuel ratio sensor to maintain oxygen concentration detection accuracy. The system detects oxygen concentration in exhaust gas and adjusts fuel injection to maintain target stoichiometry. Simultaneously, it monitors alcohol concentration and adjusts fuel injection amounts to account for alcohol's different combustion characteristics, ensuring catalyst surface reaction efficiency is optimized while preserving accurate oxygen concentration detection capability
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 device enhances the accuracy of catalyst deterioration diagnosis by accounting for variations in fuel properties and sensor signal patterns, improving the reliability of diagnosing catalyst health in engines using flexible fuels.
Implementation Method 1
a front sensor which is configured to detect a state of the exhaust gas before passing through the catalyst
Implementation Method 2
a rear sensor which is configured to detect a state of the exhaust gas after passing through the catalyst
Implementation Method 3
a catalyst which is configured to purify exhaust gas generated by combustion of the supplied flexible fuel
Data Source
AI summary
A catalyst deterioration diagnostic device generates a single set of diagnostic data based on a signal of a downstream oxygen sensor in a diagnosis period, even when at least one of the cycle or amplitude of the signal of the downstream oxygen sensor is different due to a difference in the mixture ratio of flexible fuel, even when the number of reversals of the signal of the downstream oxygen sensor in the diagnosis period is smaller than the number of reversals of the signal of the upstream oxygen sensor, when a catalyst is deteriorated, and even when the signal of the downstream oxygen sensor is reversed when the catalyst is normal. The diagnostic device diagnoses the state of deterioration of the catalyst based on at least one set of the diagnostic data generated based on a signal of the downstream oxygen sensor in a total diagnosis period.