Coaxial Planetary EV Transmission for Compact Smooth Shifting
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Solution Overview
Problem
Existing electric vehicle transmissions face challenges in achieving a lightweight and compact design due to the need for synchronizing speed differences between axes, leading to potential shift shocks and inefficiencies, and are limited by their large volume and weight.
Innovation Solution
A vehicle transmission design featuring a driving sun gear connected to a motor, a first sun gear, and a second sun gear, with a planetary gear system that meshes with these gears and a carrier, allowing for a coaxial input and output axis, minimizing size and weight, and incorporating a brake unit to reduce power loss during shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synchronizer ring is used to synchronize speed between input axis and output axis, then shift shock is reduced, but device complexity and weight increase
Solution Approach 1:
The patent removes the synchronizer ring from the transmission system by designing a direct meshing planetary gear structure where the sun gear and planetary gears engage directly without requiring separate synchronizing components, thereby reducing structural complexity while maintaining shift quality through precise gear geometry design
Solution Approach 2:
The patent combines the functions of speed synchronization and power transmission into a single integrated planetary gear mechanism, where the meshing between sun gear and planetary gears simultaneously achieves both power transfer and speed synchronization, eliminating the need for separate synchronizer components
2Power
If three different axes (motor axis, planetary gear unit axis, differential gear axis) are used, then gear transmission is achieved, but overall volume increases and lightweight design is limited
Solution Approach 1:
The patent employs a nested planetary gear configuration where planetary gears are arranged around the sun gear within a compact carrier structure, allowing multiple gear stages to be integrated in a concentric arrangement that minimizes radial and axial dimensions, achieving high power transmission in a compact volume
Solution Approach 2:
The patent transitions from a multi-axis spatial arrangement to a coaxial single-axis configuration by arranging the motor, planetary gear unit, and differential gear along a common rotational axis, thereby reducing the transmission to a compact cylindrical form factor that minimizes overall volume while maintaining full gear transmission capability
3Power
If three different axes are used in the transmission, then power transmission is achieved, but weight increases
Solution Approach 1:
The patent uses a nested planetary gear arrangement where planetary gears orbit the sun gear within a compact carrier, allowing multiple gear functions to be achieved with minimal material volume and reduced component count, directly lowering transmission weight while maintaining power transmission capability
Solution Approach 2:
The patent reconfigures the transmission from a multi-axis layout to a coaxial single-axis design, eliminating the need for complex bearing supports, shafts, and housing structures required for multiple separated axes, thereby significantly reducing overall transmission weight
Data Source
AI summary
Provided are a vehicle transmission and a vehicle powertrain device including the same. The present disclosure includes a driving sun gear receiving a driving force transmitted from a motor, a first sun gear having the same rotating axis as the driving sun gear, a second sun gear inserted into the first sun gear and having the same rotating axis as the first sun gear, a planetary gear provided with a plurality of stages which respectively mesh with the driving sun gear, the first sun gear, and the second sun gear, and a carrier to which the planetary gear is coupled so as to be rotatable and into which the first sun gear and the second sun gear are inserted.