Catalyst Deterioration Determination via Oxygen Storage Capacity
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Solution Overview
Problem
Existing methods for determining the deterioration of oxygen storage capacity in exhaust gas purification catalysts, such as three-way catalysts, face inaccuracies due to overly rich output characteristics from oxygen concentration sensors, especially when hydrogen molecules and rich gas components like HC are present, leading to difficulties in accurately switching air-fuel ratio modes and calculating oxygen storage capacity.
Innovation Solution
Limiting the rate of change of the air-fuel ratio during active air-fuel ratio control to ensure sufficient time for oxygen storage and release reactions, using an oxygen concentration sensor with specific measuring characteristics to reduce the influence of rich gas components, and adjusting the rate of change based on sensor response speed and exhaust gas flow rate to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the air-fuel ratio is shifted rapidly from lean to rich or vice versa during active air-fuel ratio control, then the oxygen storage capacity determination can be completed more quickly, but the oxygen storage and release reactions in the catalyst cannot proceed sufficiently, leading to inaccurate measurement results
Solution Approach 1:
The patent applies dynamics by making the air-fuel ratio shifting speed variable rather than fixed. The control system dynamically adjusts the shifting rate based on real-time feedback from the oxygen concentration sensor, allowing the system to optimize between speed and accuracy for each measurement cycle. This resolves the contradiction by enabling fast determination when conditions permit while ensuring sufficient reaction time when needed for accurate measurements.
2Ease of operation
If an oxygen concentration sensor is used to detect exhaust gas composition for active air-fuel ratio control, then the oxygen storage capacity can be calculated, but the sensor output deviates from actual air-fuel ratio due to overly rich output characteristics when hydrogen molecules and rich gas components are present
Solution Approach 1:
The patent implements feedback by continuously monitoring the oxygen concentration sensor output and using this information to adjust the active air-fuel ratio control strategy. When the sensor exhibits overly rich output characteristics due to hydrogen or HC interference, the feedback mechanism detects this deviation and compensates by adjusting the control parameters, thereby maintaining measurement precision while preserving the ease of oxygen storage capacity calculation.
3Measurement precision
If the air-fuel ratio shifting control is switched at the time when oxygen storage limit or release limit is reached, then accurate oxygen storage capacity determination can be achieved, but the switching timing becomes inaccurate when the oxygen concentration sensor shows overly rich output characteristics
Solution Approach 1:
The patent applies preliminary action by anticipating the sensor's overly rich output characteristic and adjusting the switching criteria in advance. Instead of waiting for the sensor to indicate the actual limit is reached, the system pre-adjusts the switching threshold to account for the expected sensor deviation. This allows accurate deterioration determination without losing time due to delayed or premature switching.
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 enables more accurate determination of catalyst deterioration by reducing the influence of sensor errors and ensuring reliable oxygen storage and release processes, leading to improved accuracy in calculating oxygen storage capacity and maintaining catalyst performance.
Implementation Method 1
an oxygen concentration sensor that measures the oxygen concentration in exhaust gas flowing out of the exhaust gas purification catalyst
Implementation Method 2
a catalyst having a capability of storing oxygen, such as a three way catalyst, is capable of removing NOx and removing HC and CO by oxidation with release of oxygen stored in it
Implementation Method 3
a catalyst having a capability of storing oxygen, such as a three way catalyst, is capable of removing NOx and removing HC and CO by oxidation with release of oxygen stored in it
Data Source
AI summary
A catalyst deterioration determination system determines deterioration of an exhaust gas purification catalyst on the basis of its oxygen storage capacity. The system includes a downstream oxygen concentration sensor having characteristics by which as rich gas components in exhaust gas increase, the oxygen concentration sensor outputs a measurement value of the oxygen concentration corresponding to a richer air-fuel ratio. The system performs a rich shift mode and a lean shift mode based on the measurement value of the oxygen concentration sensor. The rate of change of the exhaust gas air-fuel ratio in at least the lean shift mode is limited to a predetermined rate of change or lower, and the rate of change of the exhaust gas air-fuel ratio in the rich shift mode is set higher than the rate of change of the exhaust gas air fuel ratio in the lean shift mode.