Lambda Control for Three-Way Catalytic Converter
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Solution Overview
Problem
Existing methods for controlling three-way catalytic converters in internal combustion engines are subject to inaccuracies, leading to higher HC and CO emissions due to lambda drift, especially when using high binary voltage settings, which can result in NOx breakdown.
Innovation Solution
Incorporating an NOx sensor with an integrated lambda probe downstream of the catalytic converter to generate electrical signals representing lambda and NH3 values, allowing for precise adjustment of lambda setpoint values upstream by calculating differences between setpoint and measured signals, and adapting NH3 setpoint values to maintain accurate emissions control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high binary voltage setpoint value is used for the lambda probe downstream of the catalytic converter, then NOx breakdown is prevented, but lambda drift occurs in the rich direction resulting in higher HC and CO emissions
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the binary voltage signal from the lambda probe downstream of the catalytic converter and using this information to dynamically adjust the lambda setpoint value upstream. When the measured binary voltage deviates from the setpoint, the system calculates a correction value and applies it to maintain accurate lambda control, thereby preventing both NOx breakdown and excessive HC/CO emissions
Solution Approach 2:
The patent dynamically changes the lambda setpoint value based on real-time measurements of the binary voltage signal. By adjusting the setpoint value within a defined range and applying correction values calculated from the difference between setpoint and measured values, the system adapts to varying operating conditions to maintain optimal emissions control
2Reliability
If a lambda probe downstream of the catalytic converter is used for monitoring, then catalytic converter functioning is monitored, but inaccuracies occur due to voltage changes causing large lambda shifts
Solution Approach 1:
The system uses feedback from the binary voltage signal to continuously correct the lambda setpoint value. The control device monitors the actual binary voltage and compares it with the setpoint, then applies correction values to maintain accurate lambda control downstream of the catalytic converter, compensating for voltage changes that would otherwise cause large lambda shifts
Solution Approach 2:
The patent replaces direct mechanical/electrical voltage measurement with a chemical sensing approach using the lambda probe to measure oxygen concentration, which is then converted to an electrical signal. This substitution allows for more stable and accurate lambda value determination by using chemical equilibrium relationships rather than direct voltage measurement
Data Source
AI summary
Various embodiments include a method for operating an internal combustion engine with a three-way catalytic converter with lambda control, comprising: monitoring a NOx sensor for a lambda value downstream of the converter; setting a threshold value determining a lambda setpoint value upstream of the converter using the difference between the setpoint value of the electrical signal and the measured electrical signal if the signal is below the threshold; if above the threshold value, determining the lambda setpoint value upstream of the converter using the difference between a NH3 setpoint value of the NOx sensor and the measured NH3 signal of the NOx sensor; and if the measured NH3 concentration is higher than the NH3 setpoint value, increasing the lambda setpoint value upstream of the converter and, if the measured NH3 concentration is lower than the NH3 setpoint value, reducing the lambda setpoint value upstream of the converter.