Catalyst Diagnosis Device Using Downstream AFR Variation
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Solution Overview
Problem
Existing catalyst deterioration diagnosis methods fail to precisely diagnose catalyst condition due to neglecting variations in Air/Fuel Ratio (AFR) on the downstream side of the catalyst, leading to incomplete assessment of catalyst deterioration.
Innovation Solution
A catalyst diagnosis device with sensors on both upstream and downstream sides of the catalyst, controlling fuel injection to alter AFR, calculating oxygen storage and purge capacities based on elapsed time, and diagnosing deterioration by comparing AFR changes across the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If oxygen purge amount and oxygen storage amount are estimated based on theoretical AFR and upstream AFR only, then the diagnosis method is simple, but the catalyst deterioration diagnosis precision is insufficient
Solution Approach 1:
The patent adds the downstream AFR measurement dimension to the diagnosis system. By introducing a second AFR sensor downstream of the catalyst and incorporating downstream AFR variations into the oxygen storage capacity calculation, the system transitions from a one-dimensional (upstream AFR only) to a two-dimensional (upstream and downstream AFR) measurement approach, thereby improving diagnosis precision without significantly increasing system complexity
Solution Approach 2:
The patent implements feedback by continuously monitoring downstream AFR and using it to correct the oxygen storage capacity calculation. The downstream AFR information is fed back into the diagnosis algorithm to dynamically adjust the catalyst deterioration assessment, ensuring that the diagnosis reflects actual catalyst performance under varying operating conditions
2Measurement precision
If downstream AFR variation is incorporated into the diagnosis, then catalyst deterioration diagnosis precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the AFR sensing system multi-functional by using the downstream AFR sensor not only for diagnosis purposes but also for real-time catalyst performance monitoring and control. The same sensor data is utilized for both diagnostic assessment and active catalyst management, thereby reducing the need for separate dedicated diagnostic hardware
Solution Approach 2:
The patent dynamically adjusts the diagnosis parameters based on operating conditions. Instead of using fixed theoretical AFR values, the system continuously adapts the oxygen storage capacity calculation based on actual measured AFR values, engine operating mode, and temperature conditions, thereby improving precision while managing complexity through adaptive parameter adjustment
Data Source
AI summary
The present invention provides a catalyst diagnosis device that enables precisely grasping a variation of AFR and diagnosing a deteriorated condition of the catalyst based on the variation. A timer counts elapsed time Tosc until downstream AFU (AFRd) meets a predetermined threshold condition when the fuel injection quantity is corrected by increasing or decreasing it so that as to the AFRu, the transition from either of leanness or richness to the other is repeated with the stoichiometric area between the leanness and the richness. An OSA calculating section calculates an Oxygen Storage Amount (OSA) as a function of the ΔAFR, Mfuel, Ne and Tosa. An OPA calculating section calculates an Oxygen Purge Amount (OPA) as a function of the ΔAFR, Mfuel, Ne and Topa. A deterioration diagnosing section diagnoses a deteriorated condition of the catalyst C on the basis of at least one of the OSA and OPA.