Urea Dosing System Flow Reversal Without 4/2-Way Valves
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Solution Overview
Problem
Existing dosing systems for urea solutions in diesel engines face issues with freezing when ambient temperatures drop, as they rely on 4/2-way valves for reversing flow direction, which can be unreliable and lead to urea solution accumulation in pipes and components.
Innovation Solution
A compact dosing system utilizing a multi-phase brushless external rotor motor to control the direction of rotation and speed, allowing the urea solution to be pumped from a storage container to the system when the engine is off, preventing freezing by reversing the flow direction without contact with the urea solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a 4/2-way valve is used to reverse flow direction for pumping urea back to storage container, then the flow direction can be reversed, but the system complexity increases and reliability decreases due to valve failure risks
Solution Approach 1:
Instead of using a valve to reverse flow direction, the invention inverts the approach by using a single-direction pump with a bypass line that allows flow to reverse direction. The pump always pumps in one direction, but the bypass valve redirects flow back to the storage container when needed, eliminating the need for a complex reversing valve in the main pump line.
Solution Approach 2:
The invention introduces a bypass line with a bypass valve as an intermediary element. This bypass line acts as a mediator that allows urea solution to be redirected from the pump outlet back to the storage container, enabling flow reversal without requiring the main pump to change direction or use a complex 4/2-way valve.
2Productivity
If the pump runs constantly at pressure to deliver urea, then dosing efficiency is improved, but urea accumulates in pipes and system components leading to freezing risk
Solution Approach 1:
The system dynamically adjusts its operation based on engine status. During engine operation, the pump delivers urea at pressure for efficient dosing. After engine shutdown, the system automatically activates the bypass line to pump urea back to the storage container, preventing accumulation in pipes and components. This dynamic switching between dosing mode and draining mode eliminates freezing risk while maintaining dosing efficiency during operation.
3Reliability
If a membrane separates delivery room from aggregate room in the pump, then urea solution does not contact drive units improving reliability, but device complexity increases
Solution Approach 1:
The invention employs a flexible membrane as a separating element between the delivery chamber and aggregate chamber. This thin film effectively prevents urea solution from contacting the drive units while maintaining a relatively simple pump structure. The membrane's flexibility allows it to conform to the pump chamber geometry without requiring complex rigid separation structures.
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
The system effectively prevents urea solution freezing by reversing the flow direction without mechanical contact, ensuring the dosing system, lines, and components remain free of urea when the engine is off, thus extending the service life and maintaining operational efficiency.
Implementation Method 1
multi-phase brushless external rotor motor (32)
Implementation Method 2
pumped from a storage container to the system when the engine is off, preventing freezing by reversing the flow direction
Data Source
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AI summary
The invention relates to a metering system for metering a liquid, comprising an electric motor (32) for setting the desired dose by changing the speed of the electric motor. Furthermore, the system comprises an eccentric drive (52, 56) for a pump (53) having two delivery directions, wherein said eccentric drive can be driven by said electric motor (32). The system also comprises a pump ring (53) made of an elastomeric material, and a stationary ring (70), which is arranged relative to the pump ring (62) and to the eccentric drive (52, 56) such that, viewed in a section running perpendicularly to the rotational axis (74) of the pump (53), a pump chamber (120) extending in the circumferential direction is formed between the stationary ring (70) and the pump ring (62). On rotation of the electric motor (32) the pump chamber (120) changes shape in order to convey a liquid to be metered through the pump chamber (120), wherein a stationary seal (142) is provided between the intake connection and the pressure connection in said pump chamber (120).