Rotor Laminated-Core Cooling for EV Transmission Drive Units
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Solution Overview
Problem
Existing electric transmission drive units face challenges in manufacturing cost and mechanical stability due to the complexity and length of central axial cooling channels in the rotor shaft, which also impair the cooling efficiency and require additional water cooling systems.
Innovation Solution
The axial coolant channels are formed directly in the rotor's laminated core, with a distributor cap positioned on the laminated core to distribute coolant effectively, reducing the length of axial bores and using transmission oil for both lubrication and cooling, eliminating the need for additional water cooling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a continuous central cooling channel is formed along the entire length of the rotor shaft, then the winding heads can be cooled effectively, but the manufacturing cost and difficulty increase significantly and the mechanical stability of the rotor shaft deteriorates
Solution Approach 1:
The continuous central cooling channel is segmented into separate cooling channels formed directly in the rotor's laminated core. This allows the rotor shaft to have a shorter axial bore that only needs to connect to the distributor cap, reducing manufacturing complexity and improving mechanical stability while maintaining effective cooling coverage through multiple distributed channels in the laminated core
Solution Approach 2:
The cooling channels are nested within the rotor's laminated core structure itself, rather than requiring a hollow rotor shaft. The distributor cap is positioned on the laminated core and connects to these embedded channels, allowing the cooling system to be integrated into the existing rotor structure without compromising the shaft's mechanical integrity
2Temperature
If a continuous central cooling channel is formed along the entire length of the rotor shaft, then the winding heads can be cooled effectively, but the mechanical stability of the rotor shaft deteriorates
Solution Approach 1:
The continuous central cooling channel is segmented into separate cooling channels formed directly in the rotor's laminated core. This allows the rotor shaft to have a shorter axial bore that only needs to connect to the distributor cap, reducing manufacturing complexity and improving mechanical stability while maintaining effective cooling coverage through multiple distributed channels in the laminated core
Solution Approach 2:
Instead of forming cooling channels along the entire axial length of the rotor shaft (one-dimensional approach), the invention forms cooling channels directly in the laminated core and uses a distributor cap to distribute coolant radially and axially (multi-dimensional approach). This eliminates the need for a long hollow shaft while achieving comprehensive cooling coverage through spatial distribution of multiple shorter channels
3Device complexity
If transmission oil is used for both lubrication and cooling, then additional water cooling systems are eliminated, but the cooling system must handle dual functions effectively
Solution Approach 1:
The invention merges the lubrication and cooling functions into a single transmission oil circulation system. The transmission oil serves dual purposes: lubricating the gear drive unit and cooling the electric motor's winding through the distributor cap and cooling channels in the laminated core. This eliminates the need for separate water cooling systems and associated components, reducing overall system complexity while maintaining reliable cooling through the integrated oil circulation path
Solution Approach 2:
The transmission oil is given universal functionality to perform both lubrication of the gear drive unit and cooling of the electric motor winding. The distributor cap and cooling channels in the laminated core enable the transmission oil to effectively deliver cooling function in addition to its primary lubrication role, eliminating the need for separate dedicated cooling systems
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 results in a more efficient, cost-effective, and robust cooling system that maintains high power density, suitable for traction drives in motor vehicles, while reducing manufacturing costs and enhancing mechanical stability.
Implementation Method 1
Radial openings are formed in the distributor cap through which the liquid coolant can be directed radially outwards onto the first winding head by centrifugal force during the rotation of the rotor shaft
Implementation Method 2
the cooling lubricant of the reduction gear of the gear drive unit can also be used for the reliable liquid cooling of the electric motor's winding
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an electric transmission drive unit (10), and a method for manufacturing such a unit, in particular for a traction drive of a motor vehicle, with an electric motor (12) comprising a stator (60) with a stator base body (61) on which an electrical winding (68) is arranged, and with a rotor (13) having a rotor shaft (14), wherein liquid coolant (30) can be guided through the rotor shaft (14) in a radial direction (7) onto a first winding head (71) of the electrical winding (68), wherein at least one axially extending coolant channel (17) is formed in a lamellar pack (18) of the rotor (13), through which liquid coolant (30) can be guided onto a second winding head (72) of the electrical winding (68).