Metering Apparatus Pump Position Detection for Reducing Agent Accuracy
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Solution Overview
Problem
Existing metering apparatuses for reducing agents in exhaust gas treatment systems lack high accuracy and precision, leading to potential environmental contamination due to excess reducing agent penetration, particularly when ammonia is used as the reducing agent.
Innovation Solution
A method utilizing a movable pump element and position transmitters to accurately meter reducing agents, such as urea solutions, into exhaust gas treatment components, ensuring precise delivery volumes with an error of less than 5%, using a combination of position detection and calculation methods to determine the quantity of reducing agent delivered between specific reversal points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metering apparatuses are used for reducing agent delivery, then the apparatus structure is simple, but the metering accuracy is insufficient leading to excess reducing agent penetration
Solution Approach 1:
The pump stroke is segmented into distinct phases (intake phase and discharge phase) with clearly defined reversal points. The position transmitter divides the continuous motion into discrete detectable positions, enabling precise measurement of the pump element's location throughout its cycle. This segmentation allows accurate determination of the delivery volume based on position changes rather than requiring complex continuous measurement systems.
Solution Approach 2:
The system performs preliminary detection of the pump element's starting position before the metering operation begins. The controller records the initial position signal and uses it as a reference point for calculating the delivery volume. This preliminary action ensures that even if the pump element starts at different positions, the metering accuracy is maintained by measuring the change from the known starting position.
2Reliability
If reducing agent is fed in large quantities to ensure sufficient conversion of pollutant components, then the conversion efficiency is improved, but environmental contamination increases due to excess reducing agent penetration
Solution Approach 1:
The system continuously monitors the actual delivery volume by detecting the pump element's position with the position transmitter and comparing it against the required reducing agent quantity. The controller adjusts the pump operation in real-time to match the exact required amount, preventing both under-dosing (which would reduce conversion efficiency) and over-dosing (which would cause environmental contamination).
Solution Approach 2:
The system dynamically adjusts the pump delivery parameters (delivery volume, timing) based on the detected position of the pump element and the calculated actual delivery volume. By changing these parameters in real-time, the system ensures that the reducing agent quantity precisely matches the requirement for converting pollutant components, eliminating excess reducing agent that would cause environmental contamination.
3Measurement precision
If high-precision metering systems are implemented to achieve accurate reducing agent delivery, then the metering accuracy is improved, but the system costs increase
Solution Approach 1:
The position transmitter serves as an intermediary device that converts the mechanical position of the pump element into electrical signals that the controller can process. This intermediary enables precise measurement using a relatively simple and cost-effective sensor rather than requiring complex measurement systems. The position transmitter provides sufficient accuracy for metering purposes while keeping the overall system cost low.
Solution Approach 2:
The invention replaces complex mechanical metering mechanisms with a combination of position detection and electronic calculation. Instead of using precision mechanical components to ensure accurate delivery, the system uses a position transmitter to detect pump element location and a controller to calculate the actual delivery volume electronically. This substitution of mechanical precision with electronic measurement and calculation significantly reduces system costs while maintaining high metering accuracy.
Data Source
AI summary
A method for operating a metering apparatus for reducing agent includes providing the metering apparatus with at least one movable pump element movable between upper and lower reversal points to convey reducing agent into an exhaust-gas treatment component, and at least one position transmitter for determining a pass of the movable pump element. In the method, a first detection of a position of the movable pump element is provided by the position encoder. Subsequently, the movable pump element is moved and reducing agent is metered into the exhaust-gas treatment component. Thereupon, a second detection of a position of the movable pump element is provided by the position encoder, and subsequently a first quantity of reducing agent which is metered between the first and second detections is determined. A metering apparatus and a motor vehicle having a metering apparatus are also provided.