Catalyst Diagnosis via Exhaust Sensor Response Control
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Solution Overview
Problem
Existing catalyst deterioration diagnosis systems face challenges in accurately diagnosing catalyst deterioration due to decreased detection responsiveness of downstream exhaust-gas sensors, leading to premature sensor replacement and reduced diagnosis accuracy, without the need for significant design changes or cost increases in the sensor design.
Innovation Solution
A deterioration diagnosis device that includes a downstream exhaust-gas sensor with a constant current supply portion and response-time detection/correction portions, which adjusts the sensor's output characteristic by applying a constant current and voltage to the electrodes, thereby enhancing detection responsiveness without incorporating auxiliary electrochemical cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an auxiliary electrochemical cell is incorporated into the downstream exhaust-gas sensor to improve detection responsiveness, then the sensor structure and manufacturing complexity increase significantly
Solution Approach 1:
The patent applies parameter changes by controlling the output characteristics of the downstream exhaust-gas sensor through voltage application. Instead of structurally modifying the sensor with auxiliary cells, the invention changes the electrical parameters (voltage levels) to optimize detection responsiveness and differentiate between sensor deterioration and catalyst deterioration.
2Measurement precision
If tight reference values are set to account for decreased sensor responsiveness, then catalyst deterioration diagnosis accuracy improves, but sensor replacement frequency increases
Solution Approach 1:
The patent implements dynamics by adaptively adjusting reference values based on the detected sensor response characteristics. Rather than using fixed tight reference values, the system dynamically modifies thresholds according to actual sensor performance, maintaining diagnosis accuracy while avoiding premature sensor replacement.
Solution Approach 2:
The invention uses feedback mechanisms to monitor sensor output characteristics and adjust diagnosis criteria accordingly. By continuously observing sensor response and comparing it against adaptive reference values, the system distinguishes between normal aging and actual catalyst deterioration, preventing unnecessary sensor replacements.
3Device complexity
If the downstream exhaust-gas sensor is used for catalyst deterioration diagnosis without responsiveness compensation, then the system simplicity is maintained, but diagnosis accuracy decreases due to sensor aging
Solution Approach 1:
The patent enables self-service by having the downstream exhaust-gas sensor perform dual functions: its primary monitoring function and an additional responsiveness self-diagnosis function. The sensor's output characteristics are analyzed to detect both catalyst deterioration and sensor aging, eliminating the need for separate responsiveness compensation devices while maintaining diagnosis accuracy.
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 solution improves the accuracy of catalyst deterioration diagnosis, extends the lifespan of downstream exhaust-gas sensors, and avoids premature replacement by enhancing detection responsiveness and differentiating between normal and deteriorated catalysts, thus reducing the need for tight reference value settings.
Implementation Method 1
The constant current supply portion applies a constant current and a voltage to the pair of electrodes to change an output characteristic of the downstream exhaust-gas sensor
Implementation Method 2
The downstream exhaust-gas sensor detects and outputs an air-fuel ratio of the exhaust gas or detects and outputs whether the exhaust gas is rich or lean
Data Source
AI summary
A deterioration diagnosis device, which performs a deterioration diagnosis of a catalyst, includes an exhaust-gas sensor provided downstream of the catalyst in a flow direction of exhaust gas such that an output value of the exhaust-gas sensor is used at least in the deterioration diagnosis. The deterioration diagnosis device further includes the constant current supply portion which applies a voltage to a sensor element of the exhaust-gas sensor to change an output characteristic of the exhaust-gas sensor, a response-time detection portion which detects a response time required for the output value of the exhaust-gas sensor to change from a rich threshold to a lean threshold, a response-time correction portion which controls the constant current supply portion to change the output characteristic of the exhaust-gas sensor so as to shorten the response time when the response time is longer than a predetermined reference time.