Catalyst Degradation Detection Using Sensor Responsiveness Correction
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Solution Overview
Problem
Existing catalyst degradation detection methods in internal combustion engines face errors due to variations in the responsiveness of post-catalyst sensors, leading to improper determination of catalyst degradation.
Innovation Solution
A catalyst degradation detection apparatus that includes pre- and post-catalyst sensors, air/fuel ratio control, calculation, and correction mechanisms to accurately determine catalyst degradation by measuring responsiveness and correcting oxygen storage amounts based on sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxygen storage amount is calculated based on the signal from the post-catalyst sensor, then the catalyst degradation can be detected, but the determination accuracy deteriorates due to variations in sensor responsiveness
Solution Approach 1:
The system measures the responsiveness of the post-catalyst sensor and uses this information to correct the calculated oxygen storage amount. The correction amount is determined based on the measured responsiveness, creating a feedback loop that compensates for sensor variations and improves detection accuracy
Solution Approach 2:
The system changes the parameter used for degradation detection from the raw oxygen storage amount to a corrected oxygen storage amount that accounts for sensor responsiveness variations. By adjusting this parameter based on measured responsiveness, the system maintains accurate degradation detection despite sensor performance variations
2Measurement precision
If the responsiveness of the post-catalyst sensor is measured and used for correction, then the determination accuracy is improved, but the device complexity increases
Solution Approach 1:
The system uses the existing post-catalyst sensor to measure its own responsiveness and perform self-correction of the oxygen storage amount calculation. This self-service approach eliminates the need for separate measurement devices or complex external correction systems
Solution Approach 2:
The post-catalyst sensor serves multiple functions: it detects oxygen concentration for catalyst degradation monitoring and simultaneously measures its own responsiveness for correction purposes. This multi-functionality reduces the need for additional components and simplifies the overall system
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
Ensures proper determination of catalyst degradation irrespective of sensor responsiveness variations, preventing errors and maintaining accuracy in catalyst health assessment.
Implementation Method 1
a pre-catalyst sensor that is provided in an exhaust passageway upstream of a catalyst and that outputs a signal based on an oxygen concentration in exhaust gas
Implementation Method 2
a post-catalyst sensor that is provided in the exhaust passageway downstream of the catalyst and that outputs a signal based on the oxygen concentration in the exhaust gas
Implementation Method 3
oxygen in the exhaust gas that passes through the catalyst is stored into the catalyst due to the foregoing oxygen storage function of the catalyst
Implementation Method 4
oxygen stored in the catalyst is desorbed and released from the catalyst into the exhaust gas due to the oxygen storage function of the catalyst
Data Source
AI summary
A catalyst degradation detection apparatus includes: calculation means for calculating, as an oxygen storage amount of a catalyst, an amount of oxygen stored into or desorbed from the catalyst during a period from when a change that corresponds to a change in an air/fuel ratio occurs in the signal of a pre-catalyst sensor to when the signal of a post-catalyst sensor reaches a criterion value regarding the change in the air/fuel ratio; catalyst degradation determination means for determining of degradation of the catalyst on the basis of the oxygen storage amount; and correction means for correcting the oxygen storage amount calculated for use for determining of degradation of the catalyst more to a decrease side as a measured responsiveness of the post-catalyst sensor becomes more deteriorated relative to a reference value.