Planetary Gear Stiffness Gradient for Misalignment Control
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Solution Overview
Problem
Conventional planetary reduction gear apparatuses in aircrafts suffer from misalignment due to bending deformation of planetary shafts, leading to reduced lifespan and unbalanced contact between gears and bearings.
Innovation Solution
A planetary reduction gear apparatus with a planetary carrier having an annular base plate and back plate, where the stiffness of the base plate adjacent to one end of the planetary shaft is lower than the back plate, reducing bending deformation and misalignment by incorporating axially extending through-holes or slits, and forming hollow shafts to decrease weight and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the planetary shaft is made with high stiffness to reduce bending deformation, then the misalignment between planetary gears and sun/ring gears is reduced, but the weight of the planetary shaft increases
Solution Approach 1:
The planetary shaft is designed with non-uniform stiffness distribution along its length. The first portion (near the planetary gear) has higher stiffness to minimize bending deformation and maintain alignment precision, while the second portion (toward the carrier) has lower stiffness to reduce overall weight. This local differentiation of mechanical properties resolves the contradiction between precision and weight.
Solution Approach 2:
The shaft's geometric parameters are varied along its length to achieve different stiffness characteristics. By changing the diameter or cross-sectional area of the shaft at different positions, the invention creates a stiffness gradient that optimizes both alignment precision at the gear interface and overall weight reduction.
2Ease of manufacture
If the planetary carrier structure is simplified to reduce manufacturing complexity, then the ease of manufacture is improved, but the ability to restrain bending deformation of planetary shafts deteriorates
Solution Approach 1:
The planetary carrier incorporates localized stiffening features (such as ribs or thickened sections) positioned strategically near the planetary shaft support points. These local structural enhancements provide sufficient restraint against bending deformation without requiring a completely complex carrier design, thus maintaining ease of manufacture while achieving the required alignment precision.
3Manufacturing precision
If the stiffness of the base plate adjacent to the planetary shaft is reduced to suppress bending deformation, then the misalignment is reduced, but the structural strength of the base plate may be compromised
Solution Approach 1:
The base plate is designed with spatially varying stiffness, where the region adjacent to the planetary shaft has reduced stiffness to allow controlled movement that suppresses bending deformation and misalignment. Other regions of the base plate maintain higher stiffness and strength to ensure overall structural integrity. This local differentiation resolves the contradiction between precision and strength.
Solution Approach 2:
The base plate may utilize composite material construction or hybrid material layers that provide different mechanical properties in different directions or regions. This allows the plate to have reduced stiffness in specific areas for misalignment suppression while maintaining adequate strength through material selection and structural design.
Data Source
AI summary
A planetary reduction gear apparatus has a sun gear having external teeth; planetary gears, each having external teeth and configured to be meshed with the sun gear; planetary shafts, each being a rotation shaft of the planetary gear; a ring gear having internal teeth and configured to be meshed with the planetary gears; and a planetary carrier including an annular base plate and an annular back plate. The planetary carrier supports the planetary shafts between the annular base plate and the annular back plate and determines a relative position between planetary gears. The annular base plate is integrally formed with one end of the planetary shaft to support the one end. The annular back plate supports the other end of the planetary shaft. At least one of the planetary shaft and the planetary carrier has lower stiffness in its part adjacent to the one end of the planetary shaft than stiffness of its part adjacent to the other end thereof.