Rotor Helical Cooling Circuit for Compact Vehicle Electric Motors
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Solution Overview
Problem
There is a need in the industry to cool electric motors for motor vehicles, reduce their weight and dimensions, and increase torque and power density.
Innovation Solution
An electric motor design featuring a tubular stator with integrated cooling circuits using dielectric oil and water-glycol systems, where centrifugal force from the rotor's rotation drives fluid flow without pumps, enhancing heat removal and eliminating the need for additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling circuit is integrated into the electric motor, then cooling efficiency is improved, but device complexity increases
Solution Approach 1:
The cooling circuit is merged with the rotor structure, where the cooling channels are integrated into the rotor body itself. This eliminates the need for separate cooling components and reduces overall device complexity while maintaining effective cooling of the motor components.
Solution Approach 2:
The rotor serves dual functions: it generates mechanical rotation and simultaneously acts as a heat transfer medium through its integrated cooling channels. The rotor structure is designed to perform both propulsion and cooling functions, reducing the need for additional dedicated cooling components.
2Temperature
If pumps and additional heat exchangers are added to the cooling system, then cooling performance is improved, but weight increases
Solution Approach 1:
The rotating rotor itself generates centrifugal force that drives the coolant through the cooling channels. This self-service mechanism eliminates the need for external pumps, reducing weight while maintaining effective coolant circulation and cooling performance.
Solution Approach 2:
The mechanical pump system is replaced with a centrifugal force-driven flow system. The rotational motion of the rotor creates the necessary pressure differential to circulate coolant, substituting a complex mechanical pumping system with a simpler inertia-based flow mechanism.
3Temperature
If pumps and additional heat exchangers are added to the cooling system, then cooling performance is improved, but dimensions increase
Solution Approach 1:
The cooling channels are merged directly into the rotor structure, eliminating the need for separate heat exchangers and external cooling components. This integration reduces the overall volume and dimensions of the motor while maintaining effective cooling performance.
Solution Approach 2:
The cooling channels are nested within the rotor structure, with the coolant flow path embedded inside the rotor body. This nesting approach allows the cooling system to occupy the same spatial envelope as the rotor itself, minimizing additional volume requirements.
4Device complexity
If centrifugal force is used to drive fluid flow, then device complexity is reduced, but speed must be increased
Solution Approach 1:
The rotor's rotational motion, which is already necessary for motor operation, is utilized to generate centrifugal force for coolant circulation. This self-service approach uses the motor's own operating parameter (rotation speed) to drive the cooling system, eliminating the need for separate pumping mechanisms.
Solution Approach 2:
The rotor's rotation serves dual purposes: generating mechanical output and driving coolant flow through centrifugal force. This multi-functionality allows the same rotational motion to accomplish both propulsion and cooling system operation, though it does require sufficient rotational speed to generate adequate centrifugal pressure.
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 design achieves efficient cooling, reduces weight and dimensions, and increases torque and power density by leveraging the rotor's centrifugal force for fluid circulation, avoiding the use of pumps and additional heat exchangers.
Implementation Method 1
centrifugal force from the rotor's rotation drives fluid flow without pumps
Implementation Method 2
cooling circuits using dielectric oil and water-glycol systems, enhancing heat removal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electric motor (2) for a motor vehicle (1), comprising a stator (4), which is fixed relative to an axis (A); a rotor (3), which can rotate around said axis (A) relative to said stator (4) and is provided with a plurality of permanent magnets; and a first cooling circuit (50), through which a first heat transfer fluid can flow and which is thermally coupled to the stator and the rotor (3, 4) to remove heat from them; the first cooling circuit (50) comprises, in turn, a first branch (51) housed inside the rotor (4) and shaped like a helix.