NOx Sensor Diagnosis Without Engine State Variation
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Solution Overview
Problem
Existing NOx sensor diagnosis methods require varying the operation state of internal combustion engines, which can affect drivability and fuel consumption, and do not allow for timely and reliable trouble diagnosis without creating a diagnosis mode.
Innovation Solution
An NOx sensor trouble diagnosis device that calculates and stores exhaust NOx flow rates and concentrations, using predefined reference and follow patterns to determine the responsiveness of the NOx sensor without altering the engine's operation state, allowing for timely and reliable diagnosis without impacting drivability or fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If forced variation of exhaust gas composition is used to diagnose sensor responsiveness, then measurement precision is improved, but drivability and fuel consumption deteriorate
Solution Approach 1:
The system performs preliminary diagnosis by evaluating sensor output during normal engine operation before forced variation is applied. This preliminary assessment determines whether forced variation diagnosis is necessary, allowing responsiveness measurement without unnecessary disruption to drivability and fuel consumption
Solution Approach 2:
The diagnosis system dynamically adapts its operation mode based on preliminary diagnosis results. When the sensor responds normally during preliminary diagnosis, forced variation is avoided maintaining good drivability. When responsiveness is questionable, forced variation is activated to obtain precise measurement, creating a dynamic balance between measurement precision and ease of operation
2Measurement precision
If forced variation of exhaust gas composition is used to diagnose sensor responsiveness, then measurement precision is improved, but fuel consumption increases
Solution Approach 1:
The system performs preliminary diagnosis by evaluating sensor output during normal engine operation before forced variation is applied. This preliminary assessment determines whether forced variation diagnosis is necessary, allowing responsiveness measurement without unnecessary disruption to drivability and fuel consumption
Solution Approach 2:
Instead of always applying forced variation, the system applies it only partially - specifically when the preliminary diagnosis indicates the sensor responsiveness is questionable. This partial application of forced variation reduces fuel consumption while still achieving necessary measurement precision when needed
3Measurement precision
If diagnosis mode is created for sensor troubleshooting, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The diagnosis function is merged with the normal control operations. The control unit performs both engine control and sensor diagnosis using the same hardware resources. Diagnosis patterns are integrated into the control flow, eliminating the need for separate dedicated diagnosis hardware and reducing overall system complexity
Solution Approach 2:
The control unit serves multiple functions - it performs normal engine control operations and simultaneously executes sensor diagnosis functions. The same sensors and actuators used for normal operation are utilized for diagnosis purposes, making the system multi-functional and reducing the need for additional dedicated diagnosis components
Data Source
AI summary
A trouble diagnosis device and method for an NOx sensor for determining abnormality of an NOx sensor used in an exhaust gas purification system. The device can perform a trouble diagnosis without forcedly creating a diagnosis mode during operation of an internal combustion engine and without deterioration of drivability or fuel consumption. The device detects the time-lapse variation of the exhaust NOx flow rate suitable for diagnosis in a normal operation mode and determines whether the NOx sensor responds with following this variation.