Dual HEGO Sensor Cylinder Imbalance Detection
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Solution Overview
Problem
Modern vehicles with three-way catalysts face challenges in detecting and mitigating air-fuel imbalance faults between engine cylinders due to non-uniform exhaust flow conditions, leading to increased tailpipe emissions of carbon monoxide and nitrogen oxides.
Innovation Solution
The implementation of a method using time-aligned readings from symmetrically positioned exhaust gas oxygen sensors downstream of a catalyst to identify and mitigate air-fuel imbalance faults, involving the selection of one sensor for outer loop control and sequential fuel adjustment to individual cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single HEGO sensor is used for feedback control, then the control system is simple, but it cannot accurately detect cylinder-specific air-fuel imbalance faults due to non-uniform exhaust flow
Solution Approach 1:
The exhaust system is segmented into multiple zones with HEGO sensors positioned at different locations (upstream and downstream of the TWC). This segmentation allows each sensor to monitor specific regions of the exhaust flow, enabling detection of cylinder-specific imbalances that a single sensor would miss due to flow non-uniformity.
Solution Approach 2:
The patent adds spatial dimensionality to the monitoring system by placing sensors at multiple positions along the exhaust flow path (upstream and downstream of the catalyst). This multi-dimensional arrangement captures the non-uniform nature of exhaust flow and enables identification of which specific cylinder is imbalanced, rather than just detecting overall mixture conditions.
2Quantity of substance
If UEGO sensor is positioned to monitor exhaust flow, then it can detect overall AFR conditions, but it cannot identify specific cylinders with imbalance due to non-uniform zoned exhaust flow
Solution Approach 1:
The monitoring system is segmented into multiple measurement points with HEGO sensors positioned upstream and downstream of the TWC. This segmentation preserves cylinder-specific information that would otherwise be lost in the non-uniform exhaust flow, allowing identification of which specific cylinder has the air-fuel imbalance fault.
Solution Approach 2:
The TWC acts as an intermediary element between the upstream and downstream HEGO sensors. By comparing readings before and after the catalyst, the system can identify cylinder-specific imbalances that would be invisible to a single sensor, as the TWC's oxygen storage and release characteristics create detectable patterns in the dual-sensor readings.
3Ease of operation
If cylinder-specific air-fuel imbalance is not detected, then the control system operates normally, but tailpipe emissions of CO and NOx increase significantly
Solution Approach 1:
The system uses feedback from dual HEGO sensors to detect cylinder-specific air-fuel imbalances. When an imbalance is detected, the control system adjusts fuel delivery to the affected cylinder, creating a closed-loop control that maintains proper AFR and reduces harmful emissions while allowing normal operation under healthy conditions.
Data Source
AI summary
Systems and methods for identifying and mitigating air-fuel imbalance faults specific to an engine cylinder are provided. In one embodiment, a method comprises indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst. In this way, an air-fuel imbalance fault may be accurately detected in a non-uniform exhaust flow so that mitigating actions can be taken, resulting in reduced tailpipe emissions.