Catalyst Degradation Diagnosis Using Single Diagnostic Sensor
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Solution Overview
Problem
Current methods for diagnosing the degradation of diesel oxidation catalysts in vehicles suffer from poor accuracy and increased complexity due to the use of multiple sensors, leading to higher costs and inefficiencies in monitoring the oxidation ability of catalysts.
Innovation Solution
A method utilizing a single diagnostic sensor downstream of the catalyst to measure the NO conversion rate, defined as the ratio of nitrogen monoxide oxidized to nitrogen dioxide, allowing for real-time diagnosis of catalyst degradation by comparing the sensor output to a threshold value based on catalyst temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sensors (temperature sensor, O2 sensor, λ sensor, NOx sensor, PM sensor) are used to diagnose catalyst degradation, then the diagnostic coverage and reliability are improved, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple diagnostic functions (temperature measurement, oxygen concentration detection, air-fuel ratio monitoring, and catalyst degradation diagnosis) into a single integrated diagnostic system that uses one wide-range oxygen concentration sensor to perform all these functions through sequential measurement at different temperatures, thereby reducing system complexity while maintaining comprehensive diagnostic capability
Solution Approach 2:
The wide-range oxygen concentration sensor is designed to perform multiple functions: measuring exhaust gas temperature, detecting oxygen concentration, determining air-fuel ratio, and diagnosing catalyst degradation. This multi-functional sensor replaces what would traditionally require multiple specialized sensors, reducing system complexity while maintaining diagnostic reliability
2Device complexity
If a single wide-range oxygen concentration sensor is used to measure multiple parameters (temperature, oxygen concentration, air-fuel ratio), then the device complexity and cost are reduced, but the measurement precision may be compromised
Solution Approach 1:
The system dynamically adjusts the heating temperature of the exhaust gas sample in three distinct stages (first temperature for oxygen concentration, second temperature for air-fuel ratio, third temperature for catalyst diagnosis) based on the diagnostic parameter being measured. This dynamic temperature control allows a single sensor to achieve measurement precision comparable to multiple specialized sensors by optimizing measurement conditions for each parameter
Solution Approach 2:
The patent changes the temperature parameter of the exhaust gas sample according to the diagnostic needs: using a first temperature range for oxygen concentration measurement, a second temperature range for air-fuel ratio calculation, and a third temperature range for catalyst degradation diagnosis. This parameter change enables one sensor to accurately measure different parameters that would otherwise require different sensor types
3Speed
If fuel injection is increased to accelerate heat generation for temperature measurement, then the temperature measurement speed is improved, but fuel consumption increases
Solution Approach 1:
The system uses periodic heating cycles where the heater operates only during brief diagnostic measurement periods to heat the exhaust gas sample to the required temperatures. The heating is not continuous but occurs in periodic intervals when diagnostic data is needed, significantly reducing overall fuel consumption compared to continuous heating while still achieving fast temperature measurement when required
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 accurate and real-time diagnosis of catalyst degradation using a single sensor, reducing complexity and cost while improving diagnostic precision.
Implementation Method 1
a catalyst that oxidizes a predetermined gas component such as nitrogen monoxide
Implementation Method 2
the diagnostic sensor being configured to output an electromotive force corresponding to a NO conversion rate
Data Source
AI summary
Provided is a method for diagnosing whether an oxidation catalyst has degraded, based on an output value from one diagnostic sensor with higher accuracy. When a ratio of nitrogen monoxide that is oxidized by a catalyst and discharged downstream of the catalyst as nitrogen dioxide, with respect to nitrogen monoxide contained in an exhaust gas supplied upstream of the catalyst in an exhaust path is defined as a NO conversion rate, a diagnostic sensor configured to output an electromotive force corresponding to the NO conversion rate as a diagnostic output is provided downstream of the catalyst in the exhaust path, and whether the catalyst has degraded beyond an acceptable limit is diagnosed by comparing the diagnostic output with a threshold value predetermined depending on a temperature of the catalyst.