Aircraft Planetary Gear Bearing Geometry for Misalignment Control
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Solution Overview
Problem
Existing planetary gears in aircraft transmissions suffer from misalignment issues due to asymmetrical satellite carriers, leading to deflection, misalignment of satellite axes, and reduced service life due to sliding and pressure alterations, which affect the transmission of power and lubrication efficiency.
Innovation Solution
A planetary gear design with rolling bodies shaped as conical hourglasses and raceways with spherical surfaces, allowing the rolling bodies to maintain position during torque transmission, reducing sliding and maintaining parallel alignment, combined with a lubrication system to ensure efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional planetary gears with asymmetrical satellite carriers are used, then power transmission is achieved, but misalignment and deflection occur reducing service life
Solution Approach 1:
The patent employs spherical raceways in the rolling bearings that accommodate angular misalignment between satellite axes and sun axis. The spherical geometry allows the rolling bodies to self-align and compensate for deflection caused by asymmetrical satellite carrier design, maintaining reliable power transmission while preventing misalignment-related wear and failure
2Reliability
If rolling bodies are used to reduce sliding, then wear is reduced, but position maintenance during torque transmission becomes challenging
Solution Approach 1:
The spherical raceways work in conjunction with specifically shaped rolling bodies to maintain proper positioning during torque transmission. The curved geometry provides natural guidance and centering forces that keep rolling bodies in optimal positions while minimizing sliding contact and associated wear
3Power
If misalignment is allowed to occur, then torque transmission is simplified, but pressure distribution deteriorates affecting lubrication
Solution Approach 1:
The spherical raceways redistribute contact pressures by providing a geometrically optimal contact surface that accommodates misalignment while maintaining favorable pressure distribution. This ensures adequate lubrication film formation and prevents excessive localized stresses that would otherwise occur with conventional flat or cylindrical raceway geometries
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
The design enhances the service life and operating performance of the planetary gear by minimizing sliding and maintaining power transmission efficiency, even under conditions of reduced lubrication, thus improving the reliability and durability of aircraft transmissions.
Implementation Method 1
The rolling bodies (45; 46) are concave, shaped as an hourglass, and are in contact with the raceway (42) at the curved line (L1, L2). The straight lines (R1, R2) on which the axial ends (61, 62) of the curved line (L1, L2) of each rolling body (45; 46) lie converge in a point (S1; S2) lying on the axis (H) of the rolling body (45; 46) and on the axis (I). The bisector (T1; T2) of the angle (α1; α2) between the straight lines (R1, R2) lies in the plane (P1; P2).
Data Source
AI summary
A description is provided of a planetary gear comprising a sun rotatable around a first axis, a crown angularly fixed with respect to the first axis; two satellites that are meshing, rotatable around respective second axes; a satellite carrier rotatable around the first axis and comprising at least two first pins with respect to which the satellites are rotatable around respective second axes; and a plurality of bearings comprising: a first ring defining a first raceway that is at least partially spherical; a second ring defining a second raceway; and a plurality of rolling bodies 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 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.