Electric Drive Cooling via Segmented Housing and Thermal Bridge
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Solution Overview
Problem
Electric drives face challenges in thermal management and lubricant distribution, leading to high temperatures and heat generation due to splash losses, especially in low-speed, high-torque operations and off-road conditions, and difficulty in ensuring adequate lubrication of rotating components.
Innovation Solution
The electric drive incorporates a housing assembly with an intermediate housing part that forms a thermal bridge between the motor and gearing sections, featuring a motor-side and gearing-side jacket portion connected by an intermediate wall, allowing for effective heat transfer and lubricant circulation, reducing splash losses through a meandering coolant cavity and strategically placed lubricant chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high static oil level is selected to ensure adequate lubrication and cooling of upper mounted shafts and bearings, then lubrication reliability is improved, but splash losses increase leading to increased heat generation
Solution Approach 1:
The housing is divided into multiple chambers (first housing part, second housing part, intermediate housing part) with separate lubricant levels for different components. The first housing part containing upper mounted shafts and bearings has a lower lubricant level, while the second housing part with gearing has adequate lubricant for gear lubrication. This segmentation allows each component to receive appropriate lubrication without excessive splash losses.
Solution Approach 2:
The intermediate housing part acts as a thermal bridge and mediator between the motor and gearing sections. It includes a cooling jacket that receives coolant to actively cool the upper mounted shafts and bearings, replacing the need for high lubricant levels for cooling purposes. The intermediate housing part with its cooling channels serves as an intermediary cooling system.
2Temperature
If the electric drive dissipates heat from both the electric machine and transmission, then thermal management is improved, but the system complexity increases
Solution Approach 1:
The cooling system merges the cooling of the electric machine and the transmission into a single integrated solution. The intermediate housing part contains cooling channels that receive coolant to cool both the motor section and the gearing section. The stator cooling and the gearing cooling are combined through the common coolant circuit in the intermediate housing part, reducing the need for separate cooling systems.
Solution Approach 2:
The intermediate housing part serves multiple functions simultaneously: it acts as a structural connector between housing parts, provides thermal bridging for heat dissipation, contains cooling channels for active cooling, and supports the cooling jacket. This multi-functionality reduces overall system complexity by consolidating multiple thermal management functions into a single component.
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 configuration provides reliable cooling and lubrication, preventing excessive temperatures and extending the service life of the electric drive by efficiently dissipating heat and maintaining a low dynamic lubricant level, thus enhancing operational efficiency.
Implementation Method 1
a sealed cavity for a coolant flowing therethrough is formed between the outer face of the motor-side jacket portion and the inner face of the first housing part
Data Source
AI summary
An electric drive can comprise a housing assembly; an electric machine with a hollow shaft; a planetary gearing; and a power distribution unit having an input part and two output parts, the input part being connected to the planet carrier, one of the output parts being connected to an intermediate shaft extending through the hollow shaft; wherein the housing assembly comprises a motor-sided first housing part, a gearing-sided second housing part, and an intermediate housing part disposed therebetween, wherein the intermediate housing part includes, integrally formed, an intermediate wall, a motor-side jacket portion and a gearing-side jacket portion, wherein a sealed cavity for a coolant flowing therethrough is formed between an outer face of the motor-side jacket portion and the inner face of the first gearing part.