Catalytic Converter Oxygen Storage Estimation With Lean-Rich Cycling
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Solution Overview
Problem
Existing methods for determining the oxygen storage capacity of catalytic converters in internal combustion engines lead to increased carbon monoxide emissions, which are not effectively managed, and do not adequately control nitrogen oxide emissions.
Innovation Solution
An estimation method that utilizes a sequence of combustion phases with varying air-fuel mixtures, combined with oxygen probe signals, to calculate the oxygen storage capacity of catalytic converters, minimizing carbon monoxide emissions by ensuring the converter is fully oxygenated before switching to a rich mixture phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If combustion with rich air-fuel mixture is performed to deplete stored oxygen in the catalytic converter, then the oxygen storage capacity can be determined, but carbon monoxide emissions increase significantly
Solution Approach 1:
The patent applies preliminary action by performing combustion with lean air-fuel mixture BEFORE switching to rich mixture, ensuring the catalytic converter is pre-filled with oxygen. This preliminary oxygen storage allows the subsequent rich combustion phase to be shorter and less polluting, as the converter can quickly re-absorb CO without requiring prolonged rich operation. The method thus prepares the system in advance to minimize harmful emissions while achieving accurate OSC measurement.
Solution Approach 2:
The patent implements periodic action by alternating between lean and rich combustion phases in a controlled sequence. The system periodically switches from lean combustion (oxygen storage phase) to rich combustion (oxygen depletion and CO generation phase), and back again. This periodic cycling allows the catalytic converter to repeatedly charge and discharge oxygen, enabling accurate OSC determination through monitoring the duration and characteristics of each phase while minimizing overall CO emissions through optimized cycle timing.
2Loss of time
If the catalytic converter is not fully oxygenated before switching to rich mixture phase, then the estimation process is faster, but nitrogen oxide emissions increase and measurement accuracy decreases
Solution Approach 1:
The patent applies feedback by continuously monitoring the oxygen concentration in exhaust gases using lambda probes during the combustion process. The control unit receives real-time signals from these probes and uses them to determine when the catalytic converter has reached sufficient oxygen saturation before switching to rich mixture phase. This feedback mechanism ensures that the transition timing is optimized - not too early (which would cause NOx emissions) and not too late (which would waste time) - thereby achieving both measurement accuracy and emission control.
Solution Approach 2:
The patent replaces mechanical timing methods with electronic control and sensor-based detection. Instead of using fixed mechanical timers or predetermined intervals to control the combustion phases, the system uses electronic control units and oxygen sensors to dynamically determine the optimal switching points. This substitution allows for more precise control of the lean-rich transition timing, ensuring the catalytic converter is adequately oxygenated without excessive delay,ไป่ reducing NOx emissions while maintaining measurement speed.
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
This method reduces carbon monoxide emissions and maintains nitrogen oxide control by ensuring the catalytic converter is fully oxygenated, thereby improving the efficiency and precision of the oxygen storage capacity estimation without requiring hardware modifications or high computational power.
Implementation Method 1
A three-way catalytic converter operates by storing and releasing oxygen during the operation of the internal combustion engine
Implementation Method 2
the oxygen sensor arranged downstream of the catalytic converter senses an increase in the concentration of oxygen
Implementation Method 3
a catalytic converter with a good oxygen storage capacity can better compensate possible variations in the air-fuel ratio coming from the combustion chamber, improving the efficiency of the conversion of the harmful gases
Data Source
AI summary
An estimation method for determining the oxygen storage capacity of a first catalytic converter, which is arranged upstream of a second catalytic converter along an exhaust duct of an internal combustion engine. The estimation method provides for the steps of: carrying out an initial combustion phase, in which the combustion takes place with a lean air-fuel mixture at least until a first oxygen probe arranged downstream of the second catalytic converter signals a switch to a lean air-fuel mixture; carrying out an intermediate combustion phase immediately following the initial combustion phase and in which the combustion takes place with a rich air-fuel mixture at least until a second oxygen probe arranged downstream of the first catalytic converter signals a rich air-fuel mixture; and carrying out a final combustion phase immediately following the intermediate combustion phase and in which the combustion takes place with a lean air-fuel mixture after the second oxygen probe signals a rich air-fuel mixture and at least until the second oxygen probe signals a lean air-fuel mixture.