Nested Planetary Gearbox Layout for Compact EV Torque Split
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Solution Overview
Problem
Existing electric drive systems for motor vehicles face challenges in achieving a compact and efficient design, particularly in terms of space utilization and noise reduction, while maintaining effective torque transmission and differential functionality.
Innovation Solution
The system incorporates a nested planetary gear set configuration with a differential gear designed as a crown wheel differential, featuring a stacked arrangement of planetary gear sets and a brake switching element, along with a one-piece carrier element and axial flow engine, to achieve a compact and weight-optimized construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional electric drive systems are used, then torque transmission and differential functionality are achieved, but the system occupies excessive space and generates noise
Solution Approach 1:
The patent implements a nested planetary gear configuration where a first planetary gear set is positioned inside a second planetary gear set, both sharing a common rotational axis. This nesting arrangement allows multiple gear functions to occupy a reduced radial space while maintaining torque transmission and differential capabilities through the interconnected gear elements.
Solution Approach 2:
The patent transitions from conventional axial arrangements to a radial nesting configuration, organizing planetary gear sets in concentric layers around a central rotational axis. This dimensional reorganization packs multiple gear functions into a compact radial footprint while preserving all necessary torque transmission paths and differential functions.
2Volume of moving object
If compact design is pursued, then space requirements are reduced, but noise levels increase due to component density
Solution Approach 1:
The patent introduces a housing structure that serves as an intermediary element, acoustically isolating the nested planetary gear sets from the external environment. The housing encloses the compact gear arrangement, preventing noise generation from the dense component packing while allowing the compact design to maintain its space-saving advantages.
3Reliability
If multiple planetary gear sets are used for torque distribution, then differential functionality is improved, but device complexity increases
Solution Approach 1:
The patent designs the nested planetary gear sets so that each gear element serves multiple functions: the first planetary gear set handles primary torque distribution while the second set provides differential functionality, and both sets share common structural elements like the rotational axis and housing connections. This multi-functionality reduces the effective complexity despite having multiple gear sets.
Solution Approach 2:
The patent merges the functional requirements of multiple planetary gear sets into a unified nested configuration where gear elements from different sets interact through shared components. The first and second planetary gear sets are combined through common mounting structures and coordinated torque paths, reducing the number of independent mechanisms needed while maintaining enhanced differential functionality.
Data Source
AI summary
An electric drive system for a motor vehicle includes an electric engine having a stator and a rotor, and a planetary gearbox having a first planetary gear set, which has a first sun gear, a first planetary carrier, and a first ring gear. A second planetary gear set, which has a second sun gear, a second planetary carrier, and a second ring gear, is arranged radially outside and axially overlapping the first planetary gear set with regard to a rotational axis of the planetary gearbox. A differential gear includes a first crown wheel, a second crown wheel, and pinion gears arranged axially between the crown wheels and meshing with these.