Planetary Gear Torque Capacity via Axial Stacking
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Solution Overview
Problem
Existing planetary reduction gear devices face limitations in increasing torque capacity without expanding the outer diameter, as widening tooth width leads to uneven load distribution and reduced shaft strength.
Innovation Solution
The design incorporates first and second planetary gears with narrow tooth widths arranged axially, supported by coaxially fixed carriers, preventing uneven load distribution and maintaining shaft strength by keeping planetary shafts short.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tooth width of planetary gears is widened to increase torque capacity, then the torque capacity is improved, but the tooth-trace load distribution becomes uneven and planetary shaft strength decreases
Solution Approach 1:
The patent transitions from increasing torque capacity in the radial direction (wider tooth width) to the axial direction by stacking multiple planetary gears with narrow tooth widths. This dimensional shift allows achieving high torque capacity while maintaining uniform load distribution and short shaft lengths, as each planetary gear in the stack contributes additively to the total torque capacity without compromising the other detrimental effects.
2Area of stationary object
If the outer diameter of the planetary reduction gear device is restricted, then the compactness is improved, but the torque capacity cannot be increased beyond a certain limit
Solution Approach 1:
The patent overcomes the torque capacity limit imposed by outer diameter restrictions by exploiting the axial dimension. Multiple planetary gears with narrow tooth widths are stacked in the axial direction, allowing the device to maintain a compact outer diameter while achieving high torque capacity through the cumulative effect of multiple gear stages along the axis.
Solution Approach 2:
The invention employs a nested arrangement where multiple planetary gears are stacked concentrically along the axial direction, similar to nested dolls. This nesting strategy allows maximizing the use of available space within the restricted outer diameter by utilizing the axial dimension, thereby achieving high torque capacity without increasing the radial footprint.
Data Source
AI summary
A planetary reduction gear device has first and second planetary gears meshed with a sun gear and an internal at different locations in a direction of an axis line; and a carrier assembly for supporting the first and second planetary gears. The carrier assembly has a first planetary carrier for supporting the first planetary gears and a second planetary carrier for supporting the second planetary gears. The first and second planetary carriers are fixed coaxially with each other in the direction of the axis line so as to rotate integrally. A planetary reduction gear device having a large torque capacity can be obtained.