Electric Drive Unit Housing That Isolates Motor Bending Loads
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Solution Overview
Problem
Existing electric drive units face issues with cyclic bending stresses on components due to beaming loads, which can lead to fatigue and potential damage to externally mounted cooling system components.
Innovation Solution
The electric drive unit design includes a housing assembly that segregates bending loads from the stator, with a motor housing spaced apart from the perimeter wall and axle tube mount, and incorporates a lubrication and cooling system that isolates the motor assembly from these loads, using an intermediate housing member to separate cavities and employ a plate-and-frame heat exchanger for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the electric motor housing is used as a structural element to transmit beaming loads, then the weight of the electric drive unit is reduced and integration is improved, but cyclic bending stresses cause fatigue on motor components and potential damage to cooling system components
Solution Approach 1:
The housing is segmented into a load-bearing housing portion that transmits beaming loads and a motor assembly portion that is isolated from these loads. The motor housing is spaced apart from the perimeter wall and axle tube mount, creating a separation between the structural load path and the motor components. This segmentation allows the housing to serve as a structural element while protecting motor components from cyclic bending stresses.
Solution Approach 2:
An intermediate housing member is introduced as a mediator between the load-bearing structure and the motor assembly. This intermediate member provides a mounting surface for the motor housing while isolating it from the beaming loads transmitted through the housing. The intermediate housing member acts as a buffer that prevents direct transmission of cyclic bending stresses to the motor components.
2Device complexity
If cooling system components are mounted to the exterior of the housing assembly, then integration is simplified, but they are at risk of damage if they strike objects during vehicle operation
Solution Approach 1:
The cooling system components are extracted from the exterior mounting location and repositioned to the interior of the housing assembly. Specifically, the heat exchanger is positioned within the housing, surrounded by the lubricant reservoir, removing it from external exposure to potential impacts while maintaining its cooling function through thermal conduction and convection with the lubricant.
Solution Approach 2:
The cooling system components, particularly the heat exchanger, are nested within the housing assembly structure. The heat exchanger is positioned inside the housing and surrounded by the lubricant reservoir, creating a nested arrangement where the cooling component is protected by the housing structure while still performing its thermal exchange function.
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 reduces fatigue on motor components and protects cooling system components by isolating them from beaming loads, enhancing durability and preventing damage, while maintaining efficient cooling and lubrication.
Implementation Method 1
employ a plate-and-frame heat exchanger for efficient cooling
Data Source
AI summary
An electric drive unit having an electric motor, a differential assembly, a transmission, which transmits rotary power between the electric motor and the differential assembly, a pair of axle shafts, which are drivingly coupled to output members of the differential assembly, and a housing assembly in which the electric motor, the differential assembly, the transmission, and the axle shafts are housed. The electric motor includes a stator, a rotor and a motor housing that houses the stator and the rotor. The motor housing is fixedly coupled the housing assembly. Bending loads transmitted through the motor housing are not transmitted through the electric motor.