Oxygen Loading Determination for 3-Way Catalytic Converter
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Solution Overview
Problem
Current methods for determining the current oxygen loading of a 3-way catalytic converter in lambda-controlled internal combustion engines are inadequate, as they cannot provide information between the limiting values of oxygen storage capacity, leading to unpredictable emissions and inefficient catalytic converter diagnosis.
Innovation Solution
A method using the signals from pre-converter and post-converter lambda probes, along with air-mass flow rate measurements, to calculate the current oxygen loading and storage capacity, allowing for precise control and monitoring of oxygen levels to prevent emissions and optimize catalytic converter performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only post-converter lambda probe is used to monitor oxygen storage capacity, then device complexity is reduced, but measurement precision and information availability about current oxygen loading deteriorates
Solution Approach 1:
The monitoring function is segmented into two independent parts: pre-converter lambda probe for measuring oxygen concentration in exhaust gas, and post-converter lambda probe for monitoring catalytic converter function. This segmentation allows simultaneous acquisition of multiple parameters without increasing overall system complexity, as each probe performs a specific measurement function independently.
Solution Approach 2:
The control device acts as an intermediary that processes signals from both lambda probes and integrates them with air-mass flow rate data to calculate current oxygen loading. This intermediary processing enables derivation of additional information (current oxygen loading, oxygen storage capacity) from existing sensor data without adding physical sensors, thus improving measurement precision while maintaining device complexity at acceptable levels.
2Reliability
If rich/lean oscillating is produced for OSC-based diagnosing, then catalytic converter oxygen storage capacity can be checked, but emissions increase due to intentional rich/lean mixture fluctuations
Solution Approach 1:
The system performs preliminary calculation of current oxygen loading and oxygen storage capacity using continuous data from lambda probes and air-mass flow rate sensor. This preliminary information is available before actual diagnosing operations, allowing the system to assess catalytic converter state in advance and plan diagnosing sequences that minimize emissions by avoiding unnecessary rich/lean oscillations when the converter is already identified as faulty or when continuous monitoring suffices.
Solution Approach 2:
The system continuously monitors post-converter lambda probe signal and compares it with pre-converter signal and calculated oxygen loading. This feedback mechanism allows real-time assessment of catalytic converter performance without requiring intentional rich/lean oscillating. When the converter is functioning properly, the feedback shows consistent oxygen storage capacity, eliminating the need for disruptive diagnosing cycles and reducing emissions.
3Ease of operation
If post-converter lambda probe signal is used for trimming to compensate long-term drifting, then fuel/air ratio control is improved, but information about current oxygen loading between limiting values is lost
Solution Approach 1:
The system uses feedback from both pre-converter and post-converter lambda probes continuously to calculate current oxygen loading. This dual-probe feedback mechanism provides real-time information about oxygen concentration changes, enabling the control device to determine whether the catalytic converter is approaching its oxygen storage limits. This feedback information is integrated with trimming operations, allowing fuel/air ratio control to be adjusted based on actual oxygen loading state rather than relying solely on post-converter signal for trimming.
Solution Approach 2:
The system replaces the indirect mechanical/electrical trimming mechanism (post-converter signal only) with a computational approach that processes multiple sensor signals (pre-converter lambda, post-converter lambda, air-mass flow rate) to calculate oxygen loading. This substitution transforms the information acquisition method from direct signal-based trimming to calculated parameter-based control, preserving detailed information about current oxygen loading while maintaining ease of operation through automated computation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous determination of oxygen loading and storage capacity, improving the accuracy of catalytic converter diagnosis, reducing emissions, and allowing for more efficient regulation of the fuel/air ratio, thereby preventing breakthroughs and optimizing catalytic converter performance.
Implementation Method 1
Said probe measures the residual oxygen component contained in the exhaust gas
Implementation Method 2
the catalytic converter also contains a coating (washcoat) made of a material, for example Ce2O3 (di-cerium tri-oxide), that can briefly store oxygen and will bind or release it as and when required
Implementation Method 3
the oxygen released when the nitrogen oxides are reduced will suffice to almost completely oxidize the exhaust gas's HC and CO components into CO2 and H2O
Implementation Method 4
a device for measuring the air-mass flow rate
Data Source
AI summary
The invention relates to a method for determining the actual oxygen load of a 3-path catalyst of a lambda-controlled internal combustion engine, whereby a value for the actual oxygen load is calculated from the signal of a pre-catalyst lambda probe and the measured air mass flow rate by integration over time, whereby the post-catalyst lambda probe is initialized when the signal is interrupted.