Electric Machine Cooling via Segmented Circuits and Heat Exchanger
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Solution Overview
Problem
Existing electric machine cooling systems for motor vehicles are inefficient in dissipating heat from the stator and rotor, with known systems either using high viscosity transmission oil for both components or separate cooling circuits that do not optimize heat transfer, leading to structural inefficiencies and pressure issues.
Innovation Solution
A structurally compact electric machine design where the stator is cooled by a low-viscosity, electrically non-conductive medium through direct contact with the windings, and the rotor is cooled by a higher viscosity transmission oil using a heat exchanger to link the two cooling circuits, allowing for optimized heat transfer and reduced structural space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If high viscosity transmission oil is used to cool both the rotor and stator, then the cooling system is structurally simple, but the heat transfer efficiency from the stator is insufficient
Solution Approach 1:
The cooling system is segmented into two separate circuits: a transmission oil cooling circuit for the rotor and a motor vehicle cooling circuit for the stator. This segmentation allows each cooling medium to be optimized for its specific application, with the low-viscosity motor vehicle cooling medium providing superior heat transfer efficiency for the stator while the transmission oil handles rotor cooling.
Solution Approach 2:
A heat exchanger is introduced as an intermediary component that couples the transmission oil cooling circuit to the motor vehicle cooling circuit. This heat exchanger enables thermal coupling between the two circuits, allowing heat from the transmission oil to be transferred to the motor vehicle cooling medium, thereby improving overall cooling efficiency without requiring direct mixing of the two cooling media.
2Loss of energy
If separate cooling circuits are used for the rotor and stator, then the heat transfer efficiency is optimized, but the structural complexity and space requirements increase
Solution Approach 1:
The patent merges the separate cooling circuits for the rotor and stator by thermally coupling them through a heat exchanger. This allows the two circuits to operate independently for optimized heat transfer while being integrated into a unified cooling system, reducing the need for separate independent cooling systems and thereby reducing overall structural complexity.
Solution Approach 2:
The motor vehicle cooling circuit serves dual functions: it directly cools the stator and also serves as the cooling medium for the heat exchanger that cools the transmission oil. This multi-functionality reduces the need for completely separate cooling systems, thereby optimizing heat transfer efficiency while controlling structural complexity.
3Loss of energy
If the stator is cooled by a low viscosity cooling medium, then the heat transfer efficiency is improved, but the structural arrangement becomes more complex
Solution Approach 1:
The heat exchanger acts as an intermediary that enables the low-viscosity motor vehicle cooling medium to cool the stator efficiently while thermally coupling to the transmission oil cooling circuit. This intermediary component allows the system to achieve superior heat transfer efficiency with the low-viscosity medium without requiring a complete redesign of the overall cooling system architecture.
Solution Approach 2:
The patent applies different cooling media with different viscosities to different regions: the low-viscosity motor vehicle cooling medium is used where high heat transfer efficiency is critical (stator cooling), while the higher-viscosity transmission oil is used for rotor cooling. This local optimization of cooling medium properties improves heat transfer efficiency without requiring excessive structural complexity throughout the entire system.
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 ensures efficient and optimal cooling of both the stator and rotor, reducing power losses and structural pressures, while maintaining a compact arrangement with improved heat transfer characteristics.
Implementation Method 1
a first cooling medium makes direct contact with the stator windings... Power losses generated in the region of the stator optimally are dissipated by the direct contact of the first cooling medium with the stator windings
Implementation Method 2
A heat exchanger couples the transmission oil cooling circuit to the motor vehicle cooling circuit
Data Source
AI summary
A temperature control arrangement (1) of a motor vehicle has an electric machine (2) with a rotor (3) and a stator (4), a stator cooling arrangement with a first cooling circuit (6) for cooling the stator (4) with a first cooling medium (8) flowing in the first cooling circuit (6) that is formed by a motor vehicle cooling circuit, a rotor cooling arrangement with a second cooling circuit (7) for cooling the rotor (3) with a second cooling medium (9) flowing in the second cooling circuit (7) that is formed by a transmission oil cooling circuit, a heat exchanger (10) that thermally couples the first cooling circuit (6) and the second cooling circuit (7). The stator cooling arrangement is configured such that the first cooling medium (8) makes direct contact with the stator windings.