Planetary Gear Wavy Flange Fretting Prevention
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Solution Overview
Problem
The existing planetary gear devices in aircraft power transmission mechanisms experience misalignment due to bending deformation, leading to fretting between the ring gear and tubular support member, which is not effectively prevented without increasing the device's weight or processing cost.
Innovation Solution
A planetary gear device design featuring a wavy outward flange on the ring gear and inward flange with varying recess depths on the tubular support member, connected by bolts and nuts, reduces rigidity differences and prevents fretting by allowing the tubular support member to deform with the ring gear, while maintaining desired rigidity and reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rigidity of the flange connection between the ring gear and tubular support member is increased to prevent fretting, then fretting is prevented, but the weight of the device increases
Solution Approach 1:
The inward flange is designed with varying thickness (thin portion and thick portion) to create local differences in rigidity. The thin portion allows controlled deformation to prevent fretting, while the thick portion maintains necessary structural strength, avoiding the need to increase overall flange thickness and device weight.
Solution Approach 2:
The flange thickness parameter is varied along its radial direction, transitioning from a thin portion near the connection surface to a thick portion at the outer edge. This parameter change enables the flange to have different rigidity characteristics in different regions, preventing fretting through controlled deformation while maintaining overall structural integrity without increasing total weight.
2Reliability
If the rigidity difference between the ring gear flange and tubular support member flange is reduced to prevent fretting, then fretting is prevented, but the torque transmission capability is reduced
Solution Approach 1:
The inward flange incorporates a thin portion and a thick portion with different rigidity characteristics. The thin portion matches the rigidity of the ring gear flange to prevent fretting through controlled deformation, while the thick portion provides sufficient strength for torque transmission, thus resolving the contradiction between fretting prevention and torque transmission capability.
Solution Approach 2:
The flange is designed to dynamically adapt its rigidity response based on the applied load type. Under radial loading, the thin portion deforms to match the ring gear flange and prevent fretting. Under torsional loading, the thick portion engages to provide the necessary strength for torque transmission, achieving both objectives simultaneously.
3Reliability
If a flexible structure portion is added to the tubular support member to absorb deformation, then misalignment is prevented, but the device complexity increases
Solution Approach 1:
The flexible structure portion is merged with the inward flange of the tubular support member, forming an integrated structure. The varying thickness design of the flange inherently provides the flexible deformation capability needed to absorb misalignment, eliminating the need for separate flexible components and reducing overall device complexity.
Solution Approach 2:
The inward flange serves multiple functions: it provides structural support for torque transmission, enables controlled deformation to prevent fretting, and absorbs bending deformation to prevent misalignment. This multi-functional design eliminates the need for separate components for each function, reducing device complexity while achieving all desired outcomes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents fretting between the flange surfaces, ensures the desired rigidity for torque transmission, and reduces the overall weight of the device, enhancing its life performance and assembly efficiency.
Implementation Method 1
a displacement difference is produced between the flange of the ring gear and the flange of the tubular support member due to the above radial load, and fretting may occur between the surfaces of both flanges
Implementation Method 2
using a reamer bolt for ensuring bolt axial tension that can be transmitted with friction between both flanges
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a planetary gear device including: a sun gear; a plurality of planet gears; a ring gear; and a tubular support member connected to the ring gear so as to rotate together with the ring gear; an outward flange provided at the ring gear and projecting radially outward and extend over an entire periphery thereof; an wavy inward flange provided at the tubular support member and having a plurality of projection pieces projecting radially inward over an entire periphery thereof, the outward flange and the inward flange are fastened to each other by means of bolts and nuts, and the inward flange has a plurality of recesses formed between the plurality of projection pieces and the plurality of recesses include shallow first recesses and second recesses deeper than the first recesses such that depth of the recesses becomes greater at regular intervals.