Exhaust Gas Sensor Diagnosis Excluding Catalyst Plateau
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Solution Overview
Problem
Existing abnormality diagnosis techniques for exhaust gas sensors fail to accurately evaluate responsivity due to the influence of the sensor output plateau region caused by the catalyst layer, leading to reduced accuracy in detecting sensor deterioration.
Innovation Solution
An abnormality diagnosis device that calculates the response characteristics of the exhaust gas sensor by alternately changing the air-fuel ratio between rich and lean sides and excludes the sensor output plateau region, allowing for accurate evaluation of the sensor's response time without the plateau region's influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the response time of the exhaust gas sensor is measured including the sensor output plateau region, then the measurement is simpler and includes the full response period, but the responsivity evaluation becomes inaccurate due to the stagnant output region caused by the catalyst layer
Solution Approach 1:
The patent segments the sensor output response curve into distinct regions: the plateau region (caused by catalyst layer) and the non-plateau region. By dividing the response characteristics into these segments, the patent calculates response time only from the non-plateau region, excluding the stagnant plateau portion. This segmentation enables accurate responsivity evaluation by focusing only on the meaningful response portion while simplifying the calculation by clearly defining which regions to include or exclude.
2Reliability
If the air-fuel ratio is changed forcibly to diagnose sensor abnormality, then the diagnosis can be performed actively, but the sensor output plateau region influences the response time measurement and reduces detection accuracy
Solution Approach 1:
The patent extracts and excludes the harmful influence of the catalyst layer by identifying the sensor output plateau region as the portion affected by the catalyst layer. The response time calculation is performed by taking out (excluding) this plateau region from the measurement, thereby eliminating its harmful influence on the responsivity evaluation. This extraction approach allows accurate detection of sensor abnormality by considering only the non-plateau region where the sensor responds properly to air-fuel ratio changes.
Data Source
AI summary
An abnormality diagnosis device is for an exhaust gas sensor that detects an air-fuel ratio, or a rich or lean state of exhaust gas from an internal combustion engine and that includes a sensor element having a catalyst layer. The device includes an abnormality diagnosis unit that makes a sensor abnormality diagnosis whereby to change the air-fuel ratio alternately between a rich side and a lean side and to determine whether the exhaust gas sensor is abnormal or not based on response characteristics of the exhaust gas sensor in response to the change of the air-fuel ratio. When making the sensor abnormality diagnosis, the abnormality diagnosis unit calculates the response characteristics of the exhaust gas sensor with exclusion of a sensor output plateau region, which is a region in which an output of the exhaust gas sensor is stagnant due to the catalyst layer.