Coaxial Planetary Damping Ring for EV Gearbox NVH Isolation
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Solution Overview
Problem
Existing electrified vehicles with dual planetary coaxial assemblies face challenges in minimizing noise vibration and harshness (NVH) due to direct splining of ring gears into the housing, which leads to unwanted noise transmission to vehicle occupants.
Innovation Solution
Incorporation of a damping ring between the ring gear case support wall and the housing outer wall in the electric drive gearbox assembly, formed of elastomeric material, press-fit or retained by mechanical connections, to mitigate NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an NVH cover or blanket surrounds the electric drive gearbox assembly, then NVH is reduced, but cost increases and temperatures are elevated
Solution Approach 1:
A damping ring is introduced as an intermediary component between the ring gear support inner wall and the housing outer wall. This ring absorbs and dissipates vibration energy, blocking the transmission path of NVH from the planetary gear sets to the housing and ultimately to the vehicle occupants, while avoiding the complexity and thermal issues of surrounding blankets
Solution Approach 2:
Instead of applying a global NVH solution (surrounding blanket), the damping ring provides localized vibration mitigation at the critical interface where ring gears are supported. This targeted approach reduces NVH transmission paths specifically at the gear-housing connection points without adding overall system complexity
2Object-affected harmful factors
If an NVH cover or blanket surrounds the electric drive gearbox assembly, then NVH is reduced, but temperatures are elevated
Solution Approach 1:
The damping ring serves as a thermal and vibrational intermediary that allows heat to dissipate while blocking vibration transmission. Unlike enclosing blankets that trap heat, the ring's open structure permits thermal management while achieving NVH reduction through localized damping at vibration sources
3Ease of manufacture
If ring gears are directly splined into the housing, then assembly is simple, but NVH transmission increases
Solution Approach 1:
The damping ring is positioned between the ring gear support wall and housing outer wall as a mediator that interrupts direct vibration transmission paths. This allows the simple direct-spline configuration to be maintained while the ring blocks NVH from reaching the housing, decoupling the simplicity of assembly from the problem of vibration transmission
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 damping ring effectively reduces NVH transmission from the gearbox assembly to the vehicle occupant, providing a cost-effective and easily assembled solution.
Implementation Method 1
The damper is formed of elastomeric material. The inboard surface of the damper is tapered to complement the damper engaging surface. The damper mitigates noise vibration and harshness (NVH) of the electric drive gearbox assembly.
Implementation Method 2
The damper is press-fit within the annular channel. The damper has an inboard surface that engages a damper engaging surface on the ring gear support inner wall and an outboard surface that engages the housing outer wall.
Data Source
AI summary
An electric drive module (EDM) that generates and transfers drive torque to a driveline of an electrified vehicle is provided. The EDM includes an electric drive gearbox assembly having a housing, first and second planetary gear sets, and a damper. The housing defines a first and second pockets and an annular channel formed intermediate an outer wall of the housing and a ring gear support inner wall. The first planetary gear set is disposed in the first pocket and has a first ring gear splined to the ring gear support inner wall. The damper is disposed in the annular channel and has an inboard surface that engages a damper engaging surface on the ring gear support inner wall and an outboard surface that engages the housing outer wall. The damper mitigates noise vibration and harshness (NVH) of the electric drive gearbox assembly.