Dual Exhaust Oxygen Sensor Diagnosis via Crossover Flow Control
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Solution Overview
Problem
Existing systems struggle to accurately identify degradation in individual oxygen sensors among multiple sensors in an internal combustion engine, leading to insufficient correction values and potential engine air-fuel ratio control errors.
Innovation Solution
A diagnostic method that adjusts exhaust flow through crossover pipes using valves and monitors outer loop fuel controller outputs to determine the degradation of specific oxygen sensors by analyzing the impact of valve positions on correction values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple oxygen sensors are installed in each cylinder bank, then fuel control accuracy is improved, but difficulty in detecting and measuring individual sensor degradation increases
Solution Approach 1:
The exhaust system is segmented into separate paths for each cylinder bank, with dedicated downstream oxygen sensors for each bank. This segmentation allows independent monitoring of each sensor's performance, enabling identification of individual sensor degradation without affecting the other bank's fuel control.
Solution Approach 2:
A flow direction control valve is introduced as an intermediary component that can redirect exhaust flow. By controlling the valve position, the system can isolate specific sensor paths and use the outer loop fuel controller correction values as mediators to diagnose sensor health status based on the relationship between valve position and correction magnitude.
2Difficulty of detecting and measuring
If exhaust flow is redirected through crossover pipes, then diagnostic capability for oxygen sensors is improved, but device complexity increases
Solution Approach 1:
The flow direction control valve serves multiple functions: it redirects exhaust flow through crossover pipes for diagnostic purposes, and can also be used during normal operation to manage exhaust flow patterns. This multi-functionality reduces the need for separate dedicated diagnostic components, thereby limiting the increase in device complexity.
Solution Approach 2:
The system changes the flow direction parameter of the exhaust gas by adjusting the valve position. By manipulating this single parameter (flow direction) rather than adding multiple physical sensors or complex measurement systems, the diagnostic capability is achieved with minimal added complexity.
3Reliability
If outer loop fuel controller correction values are monitored, then oxygen sensor degradation detection is improved, but loss of information about which specific sensor is degraded increases
Solution Approach 1:
The system uses feedback from the outer loop fuel controller correction values, combined with valve position information, to infer the health status of specific oxygen sensors. By continuously monitoring the relationship between these parameters, the system can identify which sensor is degraded without requiring direct measurement of each sensor's output independently.
Solution Approach 2:
The diagnostic approach adds a new dimension to the monitoring system by incorporating valve position information as a fourth variable (alongside the four sensor outputs). This dimensional expansion allows the system to resolve the ambiguity of which sensor is degraded by analyzing the pattern of correction values in context with the valve position, effectively recovering the lost sensor identification information.
Data Source
AI summary
Systems and methods for diagnosing operation of four oxygen sensors of an engine that includes crossover pipes are described. The four oxygen sensors may include a left cylinder bank upstream oxygen sensor, a right cylinder bank upstream oxygen sensor, a left cylinder bank downstream oxygen sensor, and a right cylinder bank downstream oxygen sensor.