Coaxial Planetary and Differential Drive Integration
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Solution Overview
Problem
The integration of an electric drive or hybrid drive with a downstream reduction gear in motor vehicles is challenging due to limited available space, requiring a compact configuration that allows for efficient torque transmission and flexible transmission ratio adjustment.
Innovation Solution
A compact electric drive configuration featuring a coaxial planetary drive and differential drive, with a rotatingly driveable housing that accommodates both units, and an externally controllable clutch assembly for adjustable torque transmission, enabling flexible torque introduction and transmission ratio adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional electric drive with separate reduction gear and differential drive is used, then the torque transmission is reliable, but the space requirement increases and integration becomes difficult
Solution Approach 1:
The patent merges the reduction gear and differential drive into a single integrated unit. The planetary drive (reduction gear) and differential drive are combined such that the planet carrier of the planetary drive is directly connected to the differential carrier, creating a compact assembly that reduces overall space requirements while maintaining both reduction and differential functions
Solution Approach 2:
The patent implements a nested configuration where the planetary drive is arranged within the differential drive housing. The sun gear, planet gears, and ring gear are positioned inside the differential carrier housing, effectively nesting one mechanism within another to minimize the external footprint of the drive unit
2Ease of manufacture
If the planetary drive and differential drive are arranged separately, then each component is easy to manufacture, but the radial construction size increases
Solution Approach 1:
The planetary drive and differential drive are merged into a single coaxial assembly where the planet carrier serves as both the output of the planetary drive and the input to the differential drive, eliminating the need for separate housings and reducing radial dimensions
Solution Approach 2:
The patent transitions from a separate lateral arrangement of the planetary and differential drives to a coaxial arrangement along the same axis, utilizing the axial dimension to stack the mechanisms and thereby reducing the radial footprint of the overall drive unit
3Reliability
If the sun gear is fixed to the stationary component, then the planetary drive operates reliably, but the transmission ratio adjustment flexibility is reduced
Solution Approach 1:
The patent introduces a controllable coupling mechanism between the sun gear and the stationary component that can dynamically switch between fixed and movable states. This allows the system to transition between different operational modes: when coupled, the sun gear is fixed for reliable planetary reduction; when decoupled, the sun gear can rotate freely to enable direct drive or different transmission ratios
Data Source
AI summary
An electric drive for a motor vehicle is disclosed that comprises an electric motor and a drive unit drivable by the electric motor. The drive unit has a planetary drive and a differential drive 9, which are arranged coaxially to a rotational axis A. The planetary drive comprises a ring gear, a sun gear, a plurality of planet gears as well as a planet carrier. The ring gear is rotatingly driveable by the electric motor around the rotational axis A. The sun gear is supportable or supported relative to a stationary component against rotation. The planet carrier is connected to a differential carrier of the differential drive so as to transmit torque thereto. A motor vehicle with such an electric drive is also disclosed.