Dry-running Electric Coolant Pump with External Rotor and Vapor Membrane
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Solution Overview
Problem
Existing electric auxiliary water pumps face challenges with high costs, complex designs, and reduced service life due to issues with wet-running electric motors and moisture-sensitive rolling element bearings, which lead to leakage and efficiency problems.
Innovation Solution
A compact electric coolant pump design featuring a dry-running external rotor motor with an axial plain bearing and a vapor-permeable pressure equalization membrane, eliminating the need for a leakage space and using a double-lipped shaft seal and radial plain bearings lubricated by the coolant, which reduces leakage and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet-running electric motors with internal rotors are used, then sealing is simpler in the small pump structure, but efficiency decreases due to larger gap between stator and rotor and fluid friction on the rotor
Solution Approach 1:
The patent inverts the conventional motor configuration by using an external rotor design instead of internal rotor, and dry-running instead of wet-running. This reversal allows the rotor to be positioned outside the stator, eliminating the need for a can and reducing the gap between stator and rotor, thereby improving efficiency while maintaining sealing simplicity through the use of a shaft seal.
Solution Approach 2:
The patent changes the operational parameter from wet-running to dry-running, which eliminates fluid friction on the rotor. This parameter change, combined with the external rotor configuration, reduces the gap between stator and rotor, improving magnetic field strength and motor efficiency while simplifying sealing requirements.
2Reliability
If rolling element bearings are used to support pump shafts driven by dry-running electric motors, then axial and radial loads are absorbed with low friction, but moisture ingress causes corrosion and reduces bearing service life
Solution Approach 1:
The patent extracts the bearing from the moisture-prone environment by positioning it in a dry chamber separated from the pumped liquid by a shaft seal. This separation removes the harmful moisture factor from the bearing environment, allowing rolling element bearings to maintain their high load capacity and low friction characteristics while extending service life through protection from corrosion.
Solution Approach 2:
The shaft seal acts as an intermediary element between the wet pump chamber and the dry bearing chamber. It allows the pump shaft to pass through while preventing moisture ingress to the bearing, thus protecting the bearing from corrosion while maintaining its load-bearing capability and extending service life.
3Reliability
If shaft seals are added to protect rolling element bearings from moisture, then bearing reliability is maintained, but cost increases and service life is limited by seal wear and embrittlement
Solution Approach 1:
The shaft seal is designed to self-lubricate using the pumped liquid, which reduces wear and extends service life. The seal operates in a controlled manner where the pumped medium serves as a lubricant, reducing friction and preventing premature failure from dry friction and embrittlement.
Solution Approach 2:
The patent changes the operating parameters of the shaft seal by using the pumped liquid as a lubricant rather than operating in a dry state. This parameter change reduces friction and wear on the seal, extending its service life and maintaining bearing protection over longer periods.
4Reliability
If a leakage chamber is provided between shaft seal and water pump bearing, then leakage is collected and discharged without contacting the bearing, but additional installation space increases axial dimensions
Solution Approach 1:
The patent extracts the leakage chamber function by redirecting leakage flows away from the bearing area through carefully designed flow paths in the pump housing. This eliminates the need for a dedicated leakage collection chamber, reducing axial dimensions while still protecting the bearing from leakage through the shaft seal.
Solution Approach 2:
The patent uses hydraulic flow paths to redirect leakage automatically. The pump housing is designed with channels that guide leaked fluid away from the bearing area using pressure differentials and flow direction, eliminating the need for additional mechanical protection structures and reducing axial dimension.
5Loss of energy
If double-lipped shaft seal and radial plain bearings lubricated by coolant are used, then leakage is reduced and friction is minimized, but the design complexity increases
Solution Approach 1:
The pumped liquid serves multiple functions: it acts as the working fluid for pump operation, as lubricant for the radial plain bearings, and as cooling medium. This multi-functionality reduces the need for additional lubrication systems and simplifies the overall design while minimizing friction through effective lubrication.
Solution Approach 2:
The patent merges the lubrication function with the pump operation by using the pumped liquid itself as the lubricant for the bearings. This combination eliminates the need for separate lubrication systems and reduces design complexity while effectively minimizing friction through continuous lubrication.
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 design achieves a more efficient, cost-effective, and durable pump structure with reduced axial dimensions, minimizing leakage and extending the service life by vaporizing and safely discharging any leakage droplets, while avoiding the need for expensive seals and additional installation space.
Implementation Method 1
a vapor-permeable pressure equalization membrane
Implementation Method 2
vaporizing and safely discharging any leakage droplets
Implementation Method 3
radial plain bearings lubricated by the coolant, which reduces leakage and friction
Implementation Method 4
a double-lipped shaft seal
Data Source
Figure 1
AI summary
The invention relates to an electric coolant pump, preferably for use as a supplementary water pump in a vehicle, characterized in that a radial mounting of the shaft (4) is provided by means of a coolant-lubricated radial sliding bearing (41), which is arranged between the pump impeller (2) and the rotor (32); a dry-running electric motor (3) with a radially inner stator (31) and a radially outer rotor (32) is accommodated in a motor chamber (13) separated from the pump chamber (10); a shaft seal (5) is arranged between the radial sliding bearing (41) and the motor chamber (13); the rotor (32) is in the shape of a bell, the inner surface of which facing the shaft seal (5) and being fixed to the shaft seal (5) so as to axially overlap with the shaft (4); and the motor chamber (13) has an opening to the atmosphere, which is closed by a liquid-tight pressure equalisation membrane (6) that is permeable to vapour.