Vehicle SCR Reducing Agent Supply Device Backflow Mechanism
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Solution Overview
Problem
Current SCR systems face challenges in efficiently evacuating the urea supplying module after engine operation due to urea crystallization or freezing, requiring expensive solutions like electrically controlled backflow valves or supplementary compressed air.
Innovation Solution
A reducing agent supplying device with a power accumulator and backflow element, allowing the reducing agent to flow back to the tank after operation, utilizing a pressure control valve and restrictive valve to manage pressure and flow, ensuring efficient backflow without residual agents in the pressure lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive electrically controlled backflow valves or supplementary compressed air systems are used to evacuate the urea supplying module, then the reliability of preventing urea crystallization and freezing is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The system uses the pump's own pressure differential to automatically evacuate urea from the pressure lines back to the tank after operation. The pump creates negative pressure during shutdown that naturally draws residual urea back without requiring external evacuation systems, making the system self-servicing and eliminating complex backflow valves or compressed air systems.
Solution Approach 2:
The patent introduces a check valve as an intermediary component that automatically controls the backflow direction. The check valve allows urea to flow back to the tank during shutdown while preventing backward flow during operation, serving as a simple mechanical mediator that eliminates the need for complex electrically controlled valves or supplementary evacuation systems.
2Device complexity
If simple backflow mechanisms are used without pressure control, then the device complexity is reduced, but the manufacturing precision of metered injection deteriorates due to residual reducing agent in pressure lines
Solution Approach 1:
The check valve acts as a simple mechanical intermediary that automatically ensures complete backflow of residual urea to the tank while preventing interference with metered injection during operation. This simple component maintains injection precision by eliminating residual agent in pressure lines without adding complex control systems.
Solution Approach 2:
The patent replaces complex electrically controlled backflow valves with a simple mechanical check valve that uses the natural pressure differential during pump shutdown to drive complete backflow. This mechanical substitution maintains precision by ensuring all residual urea returns to the tank while significantly simplifying the system architecture.
3Productivity
If the pump is shutdown immediately after operation, then the productivity is improved, but the harmful factors increase due to urea crystallization or freezing in the pressure lines
Solution Approach 1:
The system performs preliminary evacuation action automatically when the pump shuts down. The check valve and pressure differential work together to draw all residual urea back to the tank before the pump fully stops, preventing crystallization and freezing in the pressure lines and enabling immediate shutdown without harmful effects.
Solution Approach 2:
The pump's own shutdown creates the negative pressure needed to evacuate residual urea automatically. The system uses its own operational characteristics to perform the evacuation function, eliminating the need for separate heating systems or extended shutdown periods, thus enabling immediate shutdown without crystallization or freezing risks.
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 provides a low-cost, efficient method for evacuating the urea supplying module, preventing crystallization and freezing, and maintaining metered injection precision by ensuring no residual reducing agent remains in the system.
Implementation Method 1
when the pump is turned on, the reducing agent is fed into the upstream chamber by the pump, and the reducing agent in the upstream chamber overcomes the elastic force of the elastic member and forces the complete or a part of the partition member to move towards the downstream chamber
Implementation Method 2
an elastic member biasing the partition member towards the upstream chamber... when the pump is turned off, the partition member is driven by the elastic member so that the complete or a part of it moves towards the upstream chamber
Implementation Method 3
a pump connected with the tank via a suction line... when the pump is turned on, the reducing agent is fed into the upstream chamber by the pump
Data Source
Figure 1
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Figure 4~5
AI summary
A vehicle SCR system and its reducing agent supplying device are disclosed. The reducing agent supplying device comprises a pump (40), an injecting assembly (70) connected with the pump (40) via a pressure line (60), and a power accumulator (50) disposed in the pressure line (60). The power accumulator (50) comprises a partition member defining upstream and downstream chambers (53, 54), an elastic member (55) biasing the partition member towards the upstream chamber (53), and a valve (63) disposed in the partition member. When the pump (40) is turned on, a reducing agent is fed into the upstream chamber (53) and forces the partition member to move towards the downstream chamber (54), so that the valve (63) is opened and the reducing agent flows into the downstream chamber (54). When the pump (40) is turned off, the partition member is driven by the elastic member (55) to move towards the upstream chamber (53), so that the reducing agent in the pressure line (60) and the injecting assembly (70) is drawn into the downstream chamber (54).