Stepped Planetary E-Beam Gearset for Compact Low-NVH EV Drives
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Solution Overview
Problem
Existing electrified vehicles face challenges in providing electric drive gearbox assemblies that satisfy packaging constraints while achieving desired gear ratios and reducing costs, particularly due to issues with pitch line velocity and noise, vibration, and harshness (NVH) caused by the size of the sun and ring gears.
Innovation Solution
The implementation of a coaxial e-beam powertrain with a stepped planetary gear set and a differential, incorporating features like a clutch or damper to manage ring gear quality and reduce NVH, and an offset configuration to minimize pitch line velocity and scuffing risks, along with final drive planetary gear sets to achieve desired gear reductions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sun gear and ring gear are made larger to achieve desired gear ratios, then the gear ratio requirements are met, but the pitch line velocity increases causing increased noise, vibration, and harshness (NVH)
Solution Approach 1:
The patent divides the single-stage planetary gearset into two separate planetary gearsets (first and second planetary gearsets) with different gear ratios. This segmentation allows each gearset to operate at optimized pitch line velocities, preventing excessive NVH while achieving the required overall gear reduction through cascaded multiplication of gear ratios.
Solution Approach 2:
The patent transitions from a single-stage to a two-stage planetary gear system, adding a dimensional aspect to the gear reduction approach. By stacking planetary gearsets in series along the power flow path, the system achieves higher overall gear ratios without increasing the size of individual gears beyond NVH-threshold dimensions.
2Adaptability or versatility
If the sun gear and ring gear are made larger to achieve desired gear ratios, then the gear ratio requirements are met, but the packaging space required increases
Solution Approach 1:
The patent nests the second planetary gearset within the same radial envelope as the first planetary gearset by using a shared carrier structure. The second sun gear is positioned concentrically within the annular space defined by the first ring gear, allowing both gearsets to occupy overlapping radial spaces and achieve high gear ratios without proportionally increasing the overall packaging footprint.
Solution Approach 2:
The patent utilizes the axial dimension by stacking planetary gearsets in series along the power flow path rather than expanding radially. This allows the system to achieve high gear ratios by multiplying reductions from multiple stages, keeping each individual stage compact while the cumulative effect provides the required overall ratio.
3Ease of manufacture
If simpler gear configurations are used to reduce cost, then manufacturing costs are reduced, but the ability to meet desired gear ratios while satisfying packaging constraints is compromised
Solution Approach 1:
The patent uses identical or similar planetary gearset modules for both the first and second stages, allowing standardized manufacturing processes, tooling, and assembly techniques to be reused. This modular universality reduces development and manufacturing costs compared to designing custom single-stage solutions, while the cascaded configuration provides the required gear ratio flexibility.
Solution Approach 2:
The patent segments the gear reduction function into two independent planetary gearsets that can be manufactured and tested separately before final assembly. This segmentation allows for optimized mass production of standardized planetary modules, reducing per-unit costs through economies of scale while the system-level configuration delivers the required gear ratios.
Data Source
AI summary
An electrified powertrain that generates and transfers drive torque to a driveline of an electrified vehicle includes an electric drive module, a planetary gear set and a differential. The electric drive module comprises a housing and an electric motor having a rotor that rotates relative to a stator that is fixed to the housing. The planetary gear set has a sun gear, a carrier and a ring gear. The ring gear is fixed to the stator and the sun gear is driven by the rotor. The differential is driven by the carrier and includes first and second side gears. The first side gear drives a first output shaft that drives a first drive wheel. The second side gear drives a second output shaft that drives a second drive wheel.