Catalyst Deterioration Detection Using Upstream Oxygen and Airflow
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Solution Overview
Problem
Conventional catalyst deterioration detection methods in internal combustion engine exhaust systems often prolong worsening exhaust characteristics by requiring significant changes in air-fuel ratios, leading to inaccurate detection and potential degradation of exhaust performance.
Innovation Solution
A deterioration detecting apparatus for a catalyst that uses intake air flow rate detection, multiple oxygen concentration sensors, and air-fuel ratio switching control to calculate and correct target oxygen amounts, allowing for precise detection of catalyst deterioration without degrading exhaust characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the air-fuel ratio is changed significantly to detect catalyst deterioration using conventional methods, then the detection accuracy is improved, but the exhaust characteristics deteriorate and the detection time is prolonged
Solution Approach 1:
The patent changes the detection parameter from downstream oxygen concentration to upstream oxygen concentration combined with intake air flow rate. This allows detection of catalyst deterioration by measuring the oxygen amount entering the catalyst before treatment, rather than measuring changes downstream after treatment. The upstream oxygen concentration and intake air flow rate are used to calculate the oxygen amount, providing accurate detection without requiring significant air-fuel ratio changes that would worsen exhaust characteristics.
Solution Approach 2:
The patent introduces an intermediary calculation method using the upstream oxygen concentration sensor and intake air flow rate data to determine the oxygen amount entering the catalyst. This intermediary approach (calculating oxygen amount as a intermediate value) allows indirect detection of catalyst performance without directly manipulating the exhaust composition, thereby avoiding deterioration of exhaust characteristics while maintaining detection accuracy.
2Difficulty of detecting and measuring
If the air-fuel ratio is changed significantly to detect catalyst deterioration, then the detection capability is improved, but the time period for worsening exhaust characteristics is prolonged
Solution Approach 1:
The patent performs preliminary measurement by placing the oxygen concentration sensor upstream of the catalyst to measure the oxygen concentration before the catalyst treats the exhaust. This preliminary action captures the oxygen amount entering the catalyst, which serves as a baseline for detecting deterioration. By measuring before treatment rather than after, the system can detect changes in catalyst performance without requiring prolonged air-fuel ratio changes, thus reducing the time exhaust characteristics are worsened.
3Measurement precision
If multiple sensors and control mechanisms are added to improve detection accuracy, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent makes the upstream oxygen concentration sensor serve multiple functions: it measures oxygen concentration for calculating the oxygen amount entering the catalyst, and also provides data for determining air-fuel ratio conditions. The ECU integrates multiple functions (detection, calculation, control decisions) into a single control unit, reducing overall system complexity while maintaining high measurement precision through multi-parameter monitoring.
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
Enables accurate and timely detection of catalyst deterioration with minimal impact on exhaust characteristics, improving determination accuracy and maintaining optimal performance.
Implementation Method 1
a first oxygen concentration sensor provided upstream of the catalyst
Implementation Method 2
a second oxygen concentration sensor provided downstream of the catalyst
Implementation Method 3
a catalyst provided in an exhaust system of an internal combustion engine for purifying exhaust gases
Data Source
AI summary
A deterioration detecting apparatus for a purifying catalyst in an exhaust system of an engine. A first oxygen concentration sensor is disposed upstream of the catalyst. A second oxygen concentration sensor is disposed downstream. An amount of oxygen flowing into the catalyst is calculated from the oxygen concentration detected by the first sensor and the detected intake air flow rate. A control command value of an air-fuel ratio is alternately switched between a first value corresponding to a lean air-fuel ratio and a second value corresponding to a rich air-fuel ratio according to a result of comparison between the calculated inflowing oxygen amount and target values. Excessive inflowing oxygen amounts are calculated. The target values are corrected with the excessive inflowing oxygen amount. A deterioration degree of the catalyst is detected based on an output of the second sensor when performing the switching of the control command value using the corrected target values.