Planetary Gear Bearing Geometry for Satellite Misalignment
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Solution Overview
Problem
The asymmetrical stiffness of satellite carriers in planetary gear transmissions for hovering aircraft leads to misalignment, reduced service life due to deflection and sliding of rolling bodies, resulting in power loss and heat generation, especially under reduced lubrication conditions.
Innovation Solution
The design incorporates rolling bearings with concave inner and spherical outer raceways and hourglass-shaped rolling bodies, which allow for angular misalignment compensation and reduced sliding, maintaining rolling motion without axial displacement during torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional rolling bearings with cylindrical rollers are used in planetary gear satellite carriers, then the structure is simple and easy to manufacture, but the asymmetrical stiffness causes misalignment, deflection, and sliding of rolling bodies under torque transmission
Solution Approach 1:
The patent applies spheroidality by replacing cylindrical rollers with hourglass-shaped rolling bodies that have curved surfaces. The rolling bodies feature a central waist section with minimal diameter and rounded transitions, allowing them to conform to the spherical raceway geometry. This curvature enables the rolling bodies to self-align and compensate for misalignment between the satellite axis and carrier pin axis, eliminating the sliding and deflection problems caused by asymmetric stiffness in conventional cylindrical roller bearings.
2Power
If the satellite carrier is designed with asymmetrical stiffness to accommodate power transmission, then torque transmission is effective, but rolling bodies experience sliding and deflection reducing service life
Solution Approach 1:
The patent applies asymmetry in a controlled manner by positioning the hourglass-shaped rolling bodies at specific angular locations around the satellite axis. The rolling bodies are arranged asymmetrically relative to the torque transmission path, with their minimal diameter sections oriented to optimize both load bearing and alignment compensation. This asymmetric arrangement allows the carrier to transmit torque effectively while the curved rolling bodies simultaneously compensate for the resulting misalignment through their geometric flexibility.
3Device complexity
If conventional cylindrical roller bearings are used, then the bearing structure is simple, but power loss and heat generation increase due to sliding of rolling bodies under reduced lubrication
Solution Approach 1:
The curved, hourglass-shaped rolling bodies create pure rolling contact with the spherical raceway surfaces, eliminating the sliding component that causes power loss and heat generation. The geometric curvature ensures that the velocity vectors at the contact points are always tangential to both surfaces, maintaining rolling motion even under reduced lubrication conditions. This reduces frictional losses and thermal generation while maintaining bearing functionality.
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 enhances the operational efficiency and longevity of planetary gears by minimizing sliding and maintaining proper alignment, reducing power loss and heat generation, even under low lubrication conditions.
Implementation Method 1
rolling bearings with concave inner and spherical outer raceways and hourglass-shaped rolling bodies, which allow for angular misalignment compensation and reduced sliding, maintaining rolling motion without axial displacement during torque transmission
Data Source
Figure 1~2
Figure 3
Figure 4~7
AI summary
A planetary gear (21) is provided comprising a sun (15) rotatable around a first axis, a crown (17) angularly fixed with respect to the first axis; two satellites (19) that are meshing, rotatable around respective second axes; a satellite carrier (30) rotatable around the first axis and comprising at least two first pins (32) with respect to which the satellites (19) are rotatable around respective third axes; and a plurality of bearings (40) comprising: a first ring (41) defining a first raceway (42) that is at least partially spherical; a second ring (43) defining a second raceway (44); and a plurality of rolling bodies (45; 46) shaped as an hourglass rolling on the first spherical raceway and a second raceway; each rolling body being in contact with the raceways at a line with axial ends (61; 63, 62; 64) lying on respective straight lines tilted between them and converging in a point lying on a median plane of the rolling body and on the second axis; the straight lines define a first angle, whose bisector lies on the first median.