Pressure-Actuated Urea Metering Valve for SCR Systems
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Solution Overview
Problem
Existing exhaust gas aftertreatment systems for heavy motor vehicles, particularly those using selective catalytic reduction (SCR), face challenges in precision and tightness of urea injection, especially when the engine is off, and require complex control systems and space-consuming drives.
Innovation Solution
A dosing system featuring a pressure-actuated diaphragm pump with an electromagnetically actuated armature, integrated with a throttle and check valves, allowing for precise urea injection without external control signals and reducing the need for electric motor-driven membrane pumps, ensuring 100% tightness even when the engine is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pressure-actuated metering valve is used, then the device complexity is reduced and no separate control is required, but the precision of urea injection may be compromised
Solution Approach 1:
The metering valve is designed to be self-regulating through pressure actuation, where the valve automatically opens when upstream pressure exceeds a predetermined threshold and closes when pressure drops below the threshold. This self-service mechanism eliminates the need for external control signals while maintaining reliable operation through inherent pressure-responsive behavior.
Solution Approach 2:
The patent replaces complex electronic control systems with a simple pressure-actuated mechanical valve mechanism. The valve uses pressure differential to automatically control its opening and closing, substituting electronic control lines and signal processing with a passive mechanical response to pressure changes.
2Productivity
If an electric motor-driven membrane pump is used, then the dosing capability is achieved, but the space required and cost increase
Solution Approach 1:
The patent extracts and eliminates the electric motor and eccentric drive components from the membrane pump system. By using a pressure-actuated valve mechanism, the design removes unnecessary mechanical drive components, reducing the overall volume and complexity while maintaining the essential dosing function.
Solution Approach 2:
The membrane pump operates autonomously by utilizing pressure differentials generated during engine operation. The pump is actuated by pressure changes in the urea supply line, eliminating the need for external electric motors or complex drive mechanisms, thereby reducing space requirements.
3Productivity
If the tank is arranged above the dosing system, then gravity-assisted flow is achieved, but tightness cannot be ensured when the engine is switched off
Solution Approach 1:
The patent applies preliminary anti-action by designing the pressure-actuated valve to counteract gravitational flow before leakage can occur. When the engine is off and the tank is positioned above the dosing system, the valve automatically closes when upstream pressure drops below the threshold, preventing gravity-induced leakage and ensuring tightness.
Solution Approach 2:
The valve system self-regulates based on pressure conditions, automatically closing to prevent leakage when the engine is off and the tank is positioned above the dosing system. This self-service mechanism ensures reliability without requiring additional control systems or complex valve mechanisms.
4Productivity
If a throttle is added between the metering pump and metering valve, then flow resistance is reduced and volumetric efficiency increases, but device complexity increases
Solution Approach 1:
The throttle component modifies the pressure parameters in the system by creating a controlled pressure drop. This parameter change optimizes the pressure differential across the metering valve, improving volumetric efficiency and reducing flow resistance without requiring complex control mechanisms.
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 solution enhances precision and tightness of urea injection, reduces space and cost, and ensures reliable operation under external disturbances, with reduced flow resistance and increased volumetric efficiency, while protecting the drive from corrosive effects and noise.
Implementation Method 1
the diaphragm being actuated by an armature of an electromagnet
Implementation Method 2
the metering valve opens as soon as the pressure in the first line is greater than the opening pressure of the metering valve
Implementation Method 3
the throttle according to the invention, unlike a check valve known from the prior art, has the property of creating pressure equalization between the delivery chamber of the metering pump and the metering valve
Data Source
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AI summary
A metering system for a liquid reducing agent is proposed, which enables precise metering of the reducing agent into the exhaust stream of an internal combustion engine. This is achieved in particular by the rapid and reliable closing of a pressure-operated metering valve 13.