Lambda Pre-control for Catalytic Converter Fill Level
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Solution Overview
Problem
Current engine control systems for three-way catalytic converters have a late recognition of impending departures from the catalytic converter window, leading to increased tailpipe emissions due to the reliance on signals from exhaust gas probes that are not always ready for operation, especially during cold starts, and lack a reliable model for accurately describing the converter's behavior across various operating conditions.
Innovation Solution
A method that uses a lambda target value pre-controlling with a replacement signal for the first exhaust gas probe, allowing early recognition and correction of impending departures from the catalytic converter window, even before the probe is operational, by activating a pilot control based on a system model that includes a catalytic converter model to manage the oxygen fill level effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control system waits for the exhaust gas probe to be ready for operation before controlling the catalytic converter, then the measurement accuracy is ensured, but the response time is delayed and emissions increase
Solution Approach 1:
The patent applies preliminary action by using a replacement signal from a pre-controlling lambda signal generator to provide lambda values before the exhaust gas probe is operationally ready. This allows the control system to begin managing the catalytic converter's oxygen storage capacity and maintaining it within the catalytic converter window earlier, without waiting for probe readiness. The replacement signal enables advance control actions that reduce emissions during the warm-up period.
Solution Approach 2:
The patent uses an intermediary approach by introducing a replacement signal as a temporary substitute for the unavailable exhaust gas probe signal. This intermediary lambda signal from the pre-controlling lambda signal generator mediates between the control system and the catalytic converter during the probe warm-up phase, allowing continuous control without direct probe measurement until the probe is ready.
2Measurement precision
If the system uses signals from the exhaust gas probe for lambda control, then the control accuracy is improved, but the system reliability deteriorates when the probe is not ready for operation
Solution Approach 1:
The system performs preliminary action by generating a pre-controlling lambda signal before the exhaust gas probe is ready. This replacement signal is derived from engine operating parameters (intake air quantity, rotational speed, load) and provides a reliable lambda estimate during cold start, ensuring continuous control functionality and system reliability without depending on the unready probe.
Solution Approach 2:
The patent uses a temporary, computationally simple replacement signal as a short-term substitute during the probe warm-up period. This disposable control approach uses basic engine parameter calculations rather than expensive or complex alternative sensors, providing adequate control reliability for the limited duration until the probe becomes operational.
3Reliability
If the catalytic converter is allowed to store oxygen for later use, then the conversion efficiency is improved during lean phases, but the NOx conversion deteriorates when the storage capacity is exceeded
Solution Approach 1:
The patent implements feedback control by continuously monitoring the modeled oxygen fill level of the catalytic converter and using this information to adjust the lambda target value. The control device calculates the oxygen storage capacity based on exhaust gas composition and flow rate, then feeds this information back to prevent over-filling. When the fill level approaches the maximum storage capacity, the system adjusts fuel injection to maintain lambda near 1, preventing breakdown and NOx emissions while still utilizing oxygen storage during lean phases.
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 approach enables timely and targeted corrections to maintain the catalytic converter within the active window, reducing tailpipe emissions and meeting stricter legal requirements with lower costs by initiating effective exhaust gas cleaning earlier and maintaining a better balanced fill level reserve.
Implementation Method 1
Through the use of a three-way catalytic converter, the named pollutant components can be converted.
Implementation Method 2
Due to the oxygen storage capacity of the three-way catalytic converter, lambda=1 may still be the case for several seconds after the three-way catalytic converter, after a rich or lean lambda has been set before the three-way catalytic converter.
Data Source
AI summary
A method for controlling a filling of an exhaust-gas component storage-device of a catalytic-converter in the exhaust-gas of an internal-combustion-engine, in which an actual fill level (θmod) of the exhaust-gas component storage-device is ascertained using a first-system model to which signals (λin,meas) of a first-exhaust-gas probe that extends into the exhaust-gas flow upstream from the catalytic-converter and that acquires a concentration of the exhaust-gas component are supplied, if this first exhaust-gas probe is ready for operation. A lambda-target-value (λin,set) for a first control-loop is specified by a lambda-target-value pilot control, and that, if the first exhaust-gas probe is not ready for operation, a replacement signal for the signal of the first exhaust-gas probe is supplied to the system-model, and the replacement signal is used in the lambda-target-value pilot control as an initial-value for the lambda-target-value. Also described is a control device for the method.