Exhaust Purification System Lambda Sensor Bypass
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Solution Overview
Problem
The existing methods for controlling NOx and SOx purges in exhaust gas purification systems face challenges in accurately maintaining the target excess-air-ratio due to insufficient oxidation of fuel by exhaust heat, leading to measurement inaccuracies with lambda sensors.
Innovation Solution
The system employs a control method that adjusts the air-fuel ratio through a combination of air-system control and injection control, using MAF target values and injection amount calculations to achieve the desired excess-air-ratio without relying on lambda sensor values, by setting target injection amounts and catalyst temperature adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If post injection or exhaust pipe injection is used to control excess-air-ratio during NOx or SOx purge, then the target excess-air-ratio can be achieved, but measurement accuracy deteriorates when fuel is not sufficiently oxidized by exhaust heat
Solution Approach 1:
The patent introduces an intermediary calculation method that uses MAF sensor data and injection amount information to estimate the excess-air-ratio, rather than relying directly on lambda sensor measurements in high-temperature conditions. This intermediary approach bridges the gap between unavailable reliable sensor data and the need for accurate control information.
Solution Approach 2:
The patent replaces the lambda sensor-based measurement system with a calculation-based system using MAF sensor and injection data. This substitution avoids the fundamental limitation of lambda sensors in high-temperature environments while maintaining the ability to control the excess-air-ratio.
2Ease of operation
If lambda sensor is used for feedback control of injection amount, then excess-air-ratio control is simplified, but measurement accuracy is insufficient when fuel oxidation by exhaust heat is inadequate
Solution Approach 1:
The patent replaces the lambda sensor measurement system with an alternative calculation system based on MAF sensor data and injection amount information. This substitution maintains control functionality while eliminating the measurement accuracy problems associated with lambda sensors in high-temperature, fuel-rich conditions.
Solution Approach 2:
The patent uses an intermediary calculation approach that processes MAF sensor data and injection information to derive excess-air-ratio estimates, serving as a mediator between the control system and the physical exhaust gas composition when direct sensing is unreliable.
3Temperature
If exhaust heat is used to oxidize fuel during purge operations, then temperature is maintained, but measurement accuracy deteriorates due to insufficient oxidation
Solution Approach 1:
The patent substitutes the lambda sensor measurement system with a calculation-based system using MAF sensor and injection data. This replacement allows the system to maintain exhaust temperature for fuel oxidation without relying on lambda sensor measurements that become inaccurate when oxidation is incomplete.
Solution Approach 2:
The patent extracts the measurement function from the lambda sensor and relocates it to a calculation-based system using other available sensors. This extraction allows the lambda sensor to be removed or rendered unnecessary, eliminating its measurement errors while preserving temperature maintenance functions.
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 effectively controls the exhaust gas to the required excess-air-ratio for NOx and SOx purges, reducing fuel consumption and ensuring accurate purge operations even when lambda sensor measurements are unreliable.
Implementation Method 1
an unburned fuel is supplied to an upstream-side oxidation catalyst by the post injection or the exhaust pipe injection to raise an exhaust temperature
Implementation Method 2
When the exhaust gas is under a lean atmosphere, the NOx occlusion reduction type catalyst occludes the NOx contained in the exhaust gas
Implementation Method 3
the NOx occlusion reduction type catalyst detoxifies the occluded NOx through reducing and purifying by hydrocarbon contained in the exhaust gas
Data Source
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AI summary
It effectively controls an exhaust gas to a target excess-air-ratio of an NOx purge or an SOx purge without using a lambda value of the exhaust gas. The exhaust purification system includes: an NOx reduction type catalyst (32) which is provided in an exhaust system of an internal combustion engine (10), and reduces and purifies NOx in an exhaust gas; and regeneration treatment units (60 and 70) which recover an NOx purification capacity of the NOx reduction type catalyst (32) by lowering an excess-air-ratio of the exhaust gas to a predetermined target excess-air-ratio, in which the regeneration treatment units (60 and 70) include target setting units (66 and 76) which set a target injection amount of at least one of a post injection and an exhaust pipe injection required for setting an excess-air-ratio of the exhaust gas to the target excess-air-ratio based on a suction air amount of the internal combustion engine, the target excess-air-ratio, and a fuel injection amount of the internal combustion engine, and an injection controller (50) which controls an injection amount of at least one of the post injection and the exhaust pipe injection based on the target injection amount input from the target setting units (66 and 76).