Planetary Gear Layout for High-Ratio Compact Power Transmission
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Solution Overview
Problem
In 1-axis type power transmission devices, there is a demand to increase the reduction ratio while minimizing the increase in size, as existing designs face challenges in compacting the axial length without compromising efficiency.
Innovation Solution
The implementation of a power transmission device configuration featuring a motor, a first planetary reduction gear with a stepless pinion, a second planetary reduction gear with a stepped pinion, and a differential gear, where the drive shaft penetrates the rotor and sun gears of both planetary reduction gears, allowing for increased reduction ratio without significant size expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a 1-axis type planetary reduction gear configuration is used, then the size in the vertical direction is reduced, but the reduction ratio is limited and difficult to increase
Solution Approach 1:
The planetary reduction gear is divided into multiple stages (first planetary reduction gear and second planetary reduction gear), each contributing to the overall reduction ratio. This segmentation allows the reduction ratio to be increased through series connection while maintaining compact vertical dimensions, as each stage operates within the same axial space rather than requiring additional vertical stacking.
2Productivity
If a stepped pinion is used in the planetary reduction gear, then the reduction ratio can be increased, but the device size increases
Solution Approach 1:
The drive shaft is arranged to penetrate through the rotor and sun gears, with components nested concentrically around the same axial line. The stepped pinion is integrated into this nested arrangement, allowing the reduction gear to achieve high reduction ratios through the stepped pinion's varying diameters while maintaining compact overall dimensions through the nested configuration of all components around the central drive shaft.
Data Source
AI summary
A power transmission device includes a motor including a rotor, a first planetary reduction gear connected downstream of the motor, a second planetary reduction gear connected downstream of the first planetary reduction gear, a differential gear connected downstream of the second planetary reduction gear, and a drive shaft connected downstream of the differential gear. The first planetary reduction gear includes a sun gear and a pinion gear that is a stepless pinion. The second planetary reduction gear includes a sun gear and a pinion gear that is a stepped pinion. The drive shafts is penetrating an inner circumference of the rotor of the motor, an inner circumference of the sun gear of the first planetary reduction gear, and an inner circumference of the sun gear of the second planetary reduction gear.