Stepped Planetary Gear Set for Large Reduction in Short Axles
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Solution Overview
Problem
Existing gear reduction mechanisms face limitations in achieving a large speed reduction ratio without increasing size, leading to interference, vibration, noise, and reduced service life due to incorrect gear meshing and increased axle distance.
Innovation Solution
A short-axle large-speed-ratio gear set structure comprising a housing, sun gear, internally-toothed ring track, planetary gear set with carrier frames, and output member, where the planetary gears have dual toothed portions for synchronized meshing and orbiting, allowing for a modularized coaxial assembly that reduces interference and enhances meshing engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gear ratio between the sun gear and the peripheral planetary gears is increased to achieve a large speed reduction ratio, then the speed reduction ratio is improved, but the outside diameter of the entire reduction device is expanded and the axle distance is increased
Solution Approach 1:
The patent employs a nested planetary gear configuration where multiple planetary gears are arranged in concentric circles around the sun gear. The first planetary gear is mounted on the sun gear, and the second planetary gear is mounted on the first planetary gear, creating a nested structure that achieves large speed reduction ratio while maintaining compact dimensions and short axle distance.
Solution Approach 2:
The patent transitions from a single-stage planetary gear arrangement to a multi-dimensional nested configuration by adding planetary gears at different radial levels. This dimensional arrangement allows the gear system to achieve higher reduction ratios without proportionally increasing the overall size or axle distance, as the gears are stacked in concentric layers rather than requiring larger radial spacing.
2Productivity
If multiple gears are individually mounted on the gear carrier to achieve large speed reduction ratio, then the speed reduction ratio is improved, but interference occurs and vibration noise is generated during operation
Solution Approach 1:
The patent merges the mounting function into a unified gear carrier structure that simultaneously supports multiple planetary gears at different levels. The gear carrier integrates the mounting features for both the first and second planetary gears, ensuring proper spacing and alignment. This unified structure prevents interference between gears and maintains smooth operation by coordinating the meshing of all planetary gears with the sun gear.
3Productivity
If the gear ratio of the first and second gears is increased to enhance speed reduction effect, then the speed reduction ratio is improved, but the range of gear ratio is limited and it is not possible to enhance the effect of speed reduction further
Solution Approach 1:
The patent segments the speed reduction function into multiple independent planetary gear stages, each with its own gear ratio. The first planetary gear provides one stage of reduction, and the second planetary gear provides an additional stage. By segmenting the overall reduction ratio into multiplicative stages (e.g., first stage ratio × second stage ratio), the system achieves a much broader and more flexible gear ratio range compared to a single-stage design.
Data Source
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AI summary
A structure includes a transmission axle (15) rotatably mounted at a center of a housing (10). The transmission axle (15) includes a sun gear (21) mounted thereon. An internally-toothed ring track (18) is fixed to an inner circumference of the housing (10). A planetary gear set (30) is arranged between the sun gear (21) and the internally-toothed ring track (18). The planetary gear set (30) includes a plurality of stepped planetary gears (33) arranged around the sun gear (21) for self-spinning and orbiting around the sun gear (21). Each stepped planetary gear (33) includes a first toothed portion (331) meshing with both the sun gear (21) and the internally-toothed ring track (18) and a second toothed portion (332) rotatable in unison with the first toothed portion (331). An output member (40) is fit over the planetary gear set (30) and includes an inner circumference formed with an internal toothed circumference (42) meshing with the second toothed portion (332) of each stepped planetary gear (33).