Two-Stage Planetary Drive for High-Torque Electric Vehicles
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Solution Overview
Problem
Existing integrated drive systems using internal rotor electric machines and single-stage planetary gearboxes fail to meet the high torque requirements and spatial constraints of large vehicles like buses and trucks, and suffer from low power density, high weight, and high cost.
Innovation Solution
A two-stage closed planetary gear transmission mechanism is employed, integrating a first-stage and a second-stage planetary gear mechanism to achieve a larger transmission ratio, allowing the use of a high-speed internal rotor electric machine with a maximum rotation speed of 10,000 r/min, and distributing torque across both stages to reduce gear forces and meet high torque output demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage planetary gearbox is used, then the structure is compact, but the transmission ratio is insufficient for large vehicles
Solution Approach 1:
The transmission mechanism is divided into two independent planetary gear stages. Each stage provides a portion of the total transmission ratio, allowing the system to achieve a much larger overall transmission ratio than a single stage could provide while maintaining compactness through modular design.
Solution Approach 2:
The second-stage planetary gear mechanism is nested within the first stage structure. The sun gear of the second stage is positioned within the ring gear of the first stage, and the planet gears of the second stage are arranged within the space occupied by the first stage components, achieving space-efficient compact design.
2Power
If an internal rotor electric machine with single-stage planetary gearbox is used, then power density increases, but torque capacity is insufficient for large vehicles
Solution Approach 1:
The torque transmission is segmented across two planetary gear stages. Each stage contributes to torque multiplication, allowing the system to achieve the high torque capacity required for large vehicles while maintaining the high power density benefits of the internal rotor electric machine.
3Device complexity
If the electric machine maximum rotation speed is limited to 1,500 r/min, then the system is simple, but the power output is insufficient
Solution Approach 1:
The maximum rotation speed parameter of the electric machine is increased from the conventional 1,500 r/min to 10,000 r/min. This parameter change enables the electric machine to generate significantly higher power output while the two-stage planetary gearbox reduces the rotational speed to appropriate levels for wheel drive.
Data Source
AI summary
An integrated drive system that includes a motor having a housing and an output shaft is disclosed. The integrated drive system further includes a planetary gear transmission mechanism having a first-stage planetary gear mechanism and a second-stage planetary gear mechanism. The first output torque of the first-stage planetary gear mechanism is transmitted to a driven object. The second output torque of the first-stage planetary gear mechanism is transmitted to the second-stage planetary gear mechanism. And the third output torque of the second-stage planetary gear mechanism is transmitted to the driven object. An electric vehicle that includes the described integrated drive system is also disclosed.