Planetary Gear Carrier Cutouts for Shaft Deflection Control
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Solution Overview
Problem
Conventional planetary gear reduction systems in aircraft experience journal shaft deflections and skewing due to torque forces, leading to improper engagements and reduced system lifespan.
Innovation Solution
The planetary gear reduction system incorporates a planet carrier with a first plate supporting one end of planet shafts and a second plate supporting the other end, connected by a cylindrical drum, featuring cutouts that reduce the rigidity of the first plate relative to the second plate, minimizing circumferential deflections and maintaining suitable gear engagements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the first plate is made rigid to support planet shafts, then structural strength is improved, but circumferential deflections of planet shafts increase due to torque forces
Solution Approach 1:
The first plate is designed with non-uniform rigidity: regions near planet shaft support locations have lower rigidity (with cutouts) to minimize deflections, while other regions maintain sufficient structural strength. This local differentiation of mechanical properties resolves the contradiction between overall strength and local stability.
Solution Approach 2:
The first plate is segmented into multiple regions by introducing cutouts between support portions. This segmentation allows each region to independently respond to torque forces, reducing cumulative deflections while maintaining overall structural integrity through the distributed design.
2Manufacturing precision
If cutouts are added to reduce rigidity and minimize deflections, then planet shaft alignment is improved, but weight of the system increases
Solution Approach 1:
The rigidity parameter of the first plate is selectively modified by introducing cutouts of specific dimensions and positions. This parameter change optimizes the balance between minimizing planet shaft deflections and controlling weight, as the cutouts reduce material while maintaining necessary structural function.
3Manufacturing precision
If the first plate rigidity is reduced to minimize deflections, then gear engagement precision is improved, but load-bearing capacity decreases
Solution Approach 1:
The first plate exhibits local quality variation where rigidity is reduced only in specific regions (with cutouts) to improve gear engagement precision, while other regions maintain higher rigidity to preserve load-bearing capacity. This spatial differentiation resolves the contradiction between precision and strength.
Solution Approach 2:
The first plate is designed to be dynamically responsive: under normal operating loads, the reduced-rigidity regions allow controlled flexibility for precise gear engagement, while the overall structure maintains sufficient stiffness to bear operational loads. This dynamic behavior balances precision and load capacity.
Data Source
AI summary
A planetary gear reduction system has a sun gear, a plurality of planet gears, a ring gear, and a planet carrier. The planet carrier has a first plate supporting one ends of planet shafts supporting the planet gears, a second plate supporting the other ends of the planet shafts, and a cylindrical drum connecting the first and second plates. The first plate has first portions supporting the one ends of the planet shafts; second portions connecting the first plate to the drum, the first and second portions being provided alternately in a circumferential direction; first cutouts each defined between the neighboring first and second portions, the first cutouts each extending radially inwardly from a circumferential edge thereof to a position adjacent a circle passing centers of the planet shafts; and second cutouts each defined radially inward of the second portion and between the neighboring two first portions, the second cutouts each extending radially inwardly from a first region outside the circle and a second region inside the circle.