Split Torque Transmission for EV Noise and Stress Reduction
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Solution Overview
Problem
Single speed ratio transmissions for electrical vehicles face challenges in reducing transmission noise, gear contact stresses, and shaft bending stresses due to all drive torque being delivered through a single set of output gears, leading to reduced efficiency.
Innovation Solution
A split torque transmission system with an electrical motor, featuring a rotor drive shaft, transfer gears, final drive pinions, and a differential ring gear, where the first and second transfer gears are independently meshed with the drive pinion and differential ring gear, respectively, and supported by a combination of fixed and free bearings, allowing for load sharing and reduced shaft bending stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all drive torque is delivered through a single set of output gears, then the transmission structure is simple, but gear noise and gear contact stresses increase
Solution Approach 1:
The patent divides the single torque path into multiple parallel torque paths by introducing a split torque mechanism with first and second final drive pinions. This segmentation distributes the drive torque across multiple gear contact points, reducing the load on each individual gear set and thereby reducing gear noise and contact stresses while maintaining overall structural simplicity.
2Device complexity
If all drive torque is delivered through a single set of output gears, then the transmission structure is simple, but shaft bending stresses increase
Solution Approach 1:
The split torque mechanism segments the torque transmission into multiple paths through first and second transfer gears and corresponding final drive pinions. This segmentation distributes the bending loads across multiple shafts and bearing supports, reducing the maximum bending stress experienced by any single shaft while keeping the overall transmission structure relatively simple.
3Weight of stationary object
If a single set of output gears is used, then cost and weight are reduced, but transmission output efficiency decreases
Solution Approach 1:
By segmenting the torque path into multiple parallel routes with first and second final drive pinions, the patent reduces the load and speed on each individual gear set. This segmentation lowers gear meshing losses and frictional losses in each path, improving overall transmission efficiency while adding minimal weight compared to a single heavy-duty gear set.
4Weight of stationary object
If a single set of output gears is used, then cost and weight are reduced, but gear contact stresses increase
Solution Approach 1:
The patent employs segmentation by creating multiple torque transmission paths with first and second transfer gears and final drive pinions. This distributes the contact stress across multiple gear teeth and contact points, reducing the maximum contact stress on each gear set while maintaining a lightweight transmission design.
Solution Approach 2:
The patent merges multiple torque paths into a unified output through the differential mechanism. By combining the torque from first and second final drive pinions at the differential ring gear, the system achieves both stress distribution benefits and cohesive power delivery to the wheels.
Data Source
AI summary
An automobile vehicle split torque transmission includes an electrical motor having a rotor drive shaft with a drive pinion attached to the rotor drive shaft, the rotor drive shaft defining a first axis. A first transfer gear is mounted on a first transfer gear shaft defining a second axis, the first transfer gear meshed with the drive pinion. A second transfer gear is mounted on a second transfer gear shaft defining a third axis, the second transfer gear meshed with the drive pinion. A differential ring gear is supported on a differential shaft and rotates a differential assembly, the differential shaft defining a fourth axis.