Solenoid Metering Valve Minimum Opening Duration Control
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Solution Overview
Problem
Existing systems for metering reagents into the exhaust gas area of combustion engines face challenges in achieving precise dosing, especially at lower dosage rates, which can lead to incomplete reduction of NOx gases and reagent slip, causing unnecessary consumption and odor issues.
Innovation Solution
A procedure and device that determine the minimum opening duration of a metering valve based on parameters such as reagent pressure, exhaust gas temperature, and operating voltage, using inductance modification during the opening process to ensure accurate reagent delivery, preventing crystallization and clogging, and employing a control unit with a computer program to manage the metering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the metering valve opening duration is reduced to achieve lower reagent dosage rates, then reagent consumption is optimized, but the metering precision deteriorates and spray mist quality is compromised
Solution Approach 1:
The patent applies dynamics by making the valve opening duration adaptive rather than fixed. The control unit dynamically adjusts the opening duration based on the desired dosage rate, ensuring that even at low dosage rates, the valve remains open long enough to maintain proper spray mist quality and metering precision. This dynamic adjustment resolves the contradiction between reducing dosage and maintaining precision.
Solution Approach 2:
The patent changes the temporal parameter (opening duration) of the valve operation to optimize both low dosage rates and metering precision. By extending the minimum opening duration threshold, the system ensures that the valve operates in a regime where spray mist formation is adequate, thereby maintaining manufacturing precision even when dosing small quantities of reagent.
2Reliability
If the reagent dosage is increased to ensure complete NOx reduction, then conversion efficiency is improved, but reagent slip increases causing consumption loss and odor nuisance
Solution Approach 1:
The patent implements feedback control where the control unit continuously monitors exhaust gas parameters (such as NOx concentration, temperature, and flow rate) and adjusts the reagent dosage accordingly. This closed-loop control ensures that the precise amount of reagent needed for complete NOx reduction is dosed, avoiding both under-dosing (incomplete conversion) and over-dosing (reagent slip), thereby resolving the contradiction between conversion efficiency and reagent loss.
3Manufacturing precision
If the valve opening duration is extended to improve metering accuracy, then dosing precision is enhanced, but system response time increases and productivity decreases
Solution Approach 1:
The patent applies partial action by implementing a minimum opening duration threshold rather than always using long durations. The valve is opened just long enough to ensure adequate spray mist formation and metering accuracy, avoiding unnecessarily extended opening times. This partial action approach maintains dosing precision while minimizing the impact on system response speed and productivity.
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
Ensures precise reagent metering, preventing reagent loss and crystallization, maintaining a correct spray mist at varying dosage rates, and extending the lifespan of the metering valve by determining the optimal minimum opening duration.
Implementation Method 1
a metering valve (22) which is actuated by an electromagnet (23)
Implementation Method 2
When switching the electromagnet on it attracts the armature and enables thereby an opening for metering the fuel
Implementation Method 3
The opening point of time is determined with the aid of the inductance change, which results from the attraction movement of the valve needle
Implementation Method 4
a correct spray mist is produced
Data Source
AI summary
A method is proposed for operating a metering valve which is realized as a solenoid valve which is actuated by an electromagnet that interacts with an armature which is connected fixedly to a valve needle and, furthermore, is loaded with a pulse-width modulated metering signal which defines the metering of a reagent which is to be introduced into the exhaust-gas region of an internal combustion engine or of a preliminary stage of a reagent, as is an apparatus for carrying out the method. The opening duration of the metering valve is limited to a minimum opening duration, for which the metering valve is opened completely and which is fixed in such a way that a spray mist is always produced during the metering. The procedure according to this invention prevents the reagent from crystallizing and, as a result, firstly ensures exact metering of the reagent and secondly counteracts clogging of the metering valve, in particular if a urea/water solution is provided as preliminary stage of the reagent.