Dual Pump Reductant Delivery with Overrunning Clutch Switching
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Solution Overview
Problem
Existing conveyor devices for exhaust gas aftertreatment systems, particularly in the SCR process, are structurally complex, prone to wear, and require intensive maintenance, making them costly and unreliable.
Innovation Solution
A conveyor device with two pumps connected via overrunning clutches, allowing for simple switching between delivery and suck-back states by reversing the motor direction, and utilizing a shuttle valve for hydraulic separation and a return flow restrictor to manage pressure, featuring diaphragm pumps driven by an external rotor motor for reliable and low-maintenance operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 4/2-way valve is used to switch between delivery and suck-back operations, then the reducing agent can be effectively managed, but the device complexity increases and maintenance requirements intensify
Solution Approach 1:
The patent extracts the complex 4/2-way valve from the system and replaces it with two separate pumps (delivery pump and return pump) that can be independently controlled. This removes the complex internal valve structure while maintaining the ability to switch between delivery and suck-back operations through independent pump control.
Solution Approach 2:
The patent segments the single valve function into two separate pumping functions. Instead of one complex valve handling all switching, the system divides functionality into a delivery pump for normal operation and a return pump for suck-back operations, with each pump having its own simpler control mechanism.
2Ease of operation
If multi-channel valves are used to manage fluid flow directions, then the conveying function is achieved, but the device is prone to leaks and wear
Solution Approach 1:
The patent removes the multi-channel valve entirely from the system. Instead of relying on a single valve with multiple channels that is prone to leaks and wear, the system extracts this function and implements it through two separate pumps with independent suction and discharge lines, eliminating the complex internal passages where leaks and wear occur.
Solution Approach 2:
The patent introduces separate suction and discharge lines as intermediary pathways for fluid flow. Instead of using a multi-channel valve to redirect flow internally, the system uses dedicated external lines for each pumping direction, with isolation valves positioned at strategic points to control flow without requiring complex internal valve mechanisms.
3Device complexity
If a single pump is used for both delivery and suck-back operations, then the device structure is simpler, but the switching between operations becomes complex and unreliable
Solution Approach 1:
The patent segments the single pump into two separate pumps - a delivery pump for normal operation and a return pump for suck-back operations. Each pump is optimized for its specific function and can be controlled independently, simplifying the switching mechanism to merely activating or deactivating each pump based on operational requirements.
Solution Approach 2:
While using separate pumps, the system achieves operational versatility through a common control mechanism. The control unit can independently activate the delivery pump, the return pump, or both simultaneously, providing multiple operational modes without requiring complex mechanical switching mechanisms within each pump.
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 solution provides a structurally simpler, low-maintenance, and reliable conveyor device that ensures effective ice pressure resistance and continuous supply of the reducing agent, reducing nitrogen oxide levels in exhaust gases while minimizing maintenance efforts.
Implementation Method 1
the clutches are preferably designed as overrunning clutches, but can alternatively also be designed as switchable (releasable) clutches. This makes it possible in a simple way to connect either the first pump (return pump) or the second pump (feed pump) to the drive motor and thus be powered
Implementation Method 2
the pump membrane is periodically raised and lowered by the connecting rod, whereby the reducing agent is sucked out of the storage tank and pumped to the dosing module
Implementation Method 3
An orifice plate or throttle downstream of the diaphragm pump prevents a pressure increase in the system when the dosing module is closed or only releases a very small amount of the reducing agent into the exhaust system
Implementation Method 4
During the sucking back of the reducing agent from the exhaust aftertreatment system, the conveying direction of the diaphragm pump can be maintained unchanged. Only the 4/2-way valve is activated
Data Source
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AI summary
The invention relates to a pumping device (20) for supplying an exhaust gas aftertreament system (10) of an internal combustion engine with a reductant (14), in particular with a urea-water solution, in order to reduce nitrogen oxides (NOx) in the exhaust gas flow of the internal combustion engine, comprising a motor (32) for driving two pumps (22, 24). According to the invention, the first pump (22) is connected to the motor (32) by means of a first coupling, and the second pump (24) is connected to the motor by means of a second coupling. In a preferred embodiment, the couplings are designed as freewheel couplings (26, 28) acting in opposite directions, so that a switch between a "pumping state" and a "suck-back state" can be made by simply reversing the direction of rotation of the motor (32).