Coaxial Planetary Drive Layout for Compact High-Reduction EV Transmissions
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Solution Overview
Problem
Existing vehicle drive devices face challenges in reducing size while maintaining a high reduction ratio for the planetary gear mechanism and appropriate support for the output differential gear mechanism, leading to increased radial and axial dimensions.
Innovation Solution
A vehicle drive device configuration where the planetary gear mechanism is disposed coaxially with the rotating electrical machine and output differential gear mechanism, utilizing a ring gear as the input element to the differential gear mechanism, which restricts relative movement in the radial direction, allowing for a high reduction ratio and reduced size by omitting unnecessary support members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the planetary gear mechanism is disposed radially outward of the output differential gear mechanism, then the axial dimension is reduced, but the radial dimension increases
Solution Approach 1:
The patent changes the spatial arrangement from radial disposition to axial disposition of the planetary gear mechanism. By placing the planetary gear mechanism axially adjacent to the output differential gear mechanism rather than radially outward, the invention reduces radial dimension while managing axial dimension through compact design.
2Productivity
If the carrier supports pinion gears and connects to the differential case, then the planetary gear mechanism achieves speed reduction, but the radial dimension increases
Solution Approach 1:
The patent merges the carrier of the planetary gear mechanism with the input shaft of the output differential gear mechanism. This integration allows the carrier to directly serve as the input element for the differential mechanism, achieving speed reduction while minimizing radial dimension by eliminating separate connection components.
3Reliability
If support members are added to ensure appropriate support for the output differential gear mechanism, then reliability improves, but device complexity and size increase
Solution Approach 1:
The patent makes the carrier serve multiple functions: it acts as the carrier for the planetary pinion gears, the input shaft for the output differential gear mechanism, and provides structural support for the entire assembly. This multi-functionality ensures reliable support while reducing the number of separate support members needed.
Data Source
AI summary
A first rotating element is a first sun gear that rotates with a rotor. A third rotating element is a first ring gear connected to a case. A fourth rotating element is a second ring gear that rotates with an input element. A second rotating element is a first carrier rotatably supporting a first pinion gear and a second pinion gear that rotate together. The first pinion gear meshes with the first sun gear and the first ring gear. The second pinion gear has a smaller diameter than the first pinion gear and meshes with the second ring gear. The first sun gear is supported in a radial direction with respect to the case via a first support bearing. The second ring gear and the input element are connected such that their relative movement in the radial direction is restricted.