Nested Planetary Differential for Compact High-Ratio Drivetrains
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Solution Overview
Problem
Existing drive train transmissions for motor vehicles are not radially compact and do not allow for high transmission ratios within the same installation space, leading to inefficiencies and increased weight and component count.
Innovation Solution
A transmission design featuring a differential with two planetary gear sets, where the ring gear of the first gear set is integrally bonded to a connecting component that is also connected to the sun gear of the second gear set, allowing for a radially compact and efficient torque distribution to two output shafts, reducing the number of components and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional transmission designs are used, then the transmission can transmit torque to output shafts, but the radial size is large and transmission ratio is limited within the same installation space
Solution Approach 1:
The patent implements nesting by placing the first planetary gear set inside the second planetary gear set, with the ring gear of the first gear set connected to the sun gear of the second gear set. This nested configuration allows both gear sets to occupy the same radial space, achieving a compact transmission design with high transmission ratio without increasing radial dimensions.
Solution Approach 2:
The patent transitions from a conventional parallel arrangement of gear sets to a nested axial arrangement, utilizing the axial dimension to stack multiple planetary gear sets. This dimensional reorganization enables the transmission to achieve higher ratios within the same radial envelope by exploiting the unused axial space.
2Productivity
If multiple planetary gear sets are used to increase transmission ratio, then the transmission ratio improves, but the number of components and weight increase
Solution Approach 1:
The patent merges the first and second planetary gear sets into a single integrated differential unit, where the ring gear of the first gear set is directly connected to the sun gear of the second gear set. This merging eliminates intermediate components and reduces the overall number of parts, thereby reducing weight while maintaining the high transmission ratio capability of multiple gear sets.
Solution Approach 2:
The integrated differential structure serves multiple functions simultaneously: it provides torque splitting to two output shafts, achieves high transmission ratio through nested planetary gear sets, and reduces component count. This multi-functionality allows the transmission to achieve high productivity without proportional weight increase.
3Productivity
If multiple planetary gear sets are used to increase transmission ratio, then the transmission ratio improves, but the device complexity increases
Solution Approach 1:
By nesting the first planetary gear set within the second planetary gear set, the patent reduces the spatial footprint and interconnection complexity. The shared radial space and direct connection between the ring gear of the first set and sun gear of the second set simplify the overall structure compared to conventional parallel arrangements.
Solution Approach 2:
The integration of two planetary gear sets into a single differential unit with shared components reduces the number of discrete parts and simplifies assembly. The unified structure with two output shafts emerging from a single housing reduces device complexity while maintaining high transmission ratio capability.
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 solution achieves a radially more compact transmission with higher transmission ratios, optimizing installation space and reducing weight and component count while maintaining high power density and efficiency.
Implementation Method 1
the connecting component and the ring gear of the first planetary gear set are integrally bonded
Data Source
AI summary
A transmission has a differential including a first planetary gear set having a first gear set element connected to an input shaft for conjoint rotation, a second gear set element at least indirectly connected to a first output shaft for conjoint rotation, and a third gear set element that is a ring gear. The differential further includes a second planetary gear set having a first gear set element that is a sun gear, a second gear set element non-rotationally connected to a positionally fixed component, and a third gear set element at least indirectly connected to a second output shaft for conjoint rotation. The differential also includes a connector connecting the ring gear of the first planetary gear set and the sun gear of the second planetary gear set for conjoint rotation, where the connector and the ring gear of the first planetary gear set are integrally bonded.