Grooved Pivot Pin Geometry for Bearing Alignment and Heat Dissipation
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Solution Overview
Problem
In aircraft gas turbine engines, epicyclic gear trains experience misalignment and temperature issues due to the sensitivity of sliding bearing pivot pins to lubrication and thermal conditions, leading to reduced reliability and efficiency.
Innovation Solution
A pivot pin with axially open circumferential grooves of varying width and depth is designed to provide flexibility and enhance heat dissipation, with reduced flexibility in high heating locations to minimize misalignment and temperature increases, and the pivot pin is preferably made in one piece for improved heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If circumferential grooves are made uniformly deep and wide to provide flexibility, then misalignment is reduced, but heat dissipation is impaired due to trapped air zones
Solution Approach 1:
The circumferential grooves are designed with non-uniform depth around the pivot pin circumference. Specifically, the groove depth varies angularly, being deeper in regions where flexibility is needed for alignment compensation and shallower or absent in regions requiring optimal heat dissipation. This local differentiation allows the pivot pin to simultaneously achieve both misalignment compensation and effective thermal management.
2Manufacturing precision
If circumferential grooves are made deeper to increase flexibility, then misalignment between active surface and bearing seatings is reduced, but heat conduction is limited due to air trapping
Solution Approach 1:
The groove depth is locally optimized around the pivot pin circumference. In angular regions where misalignment compensation is most needed, deeper grooves provide greater flexibility. In regions where heat dissipation is critical, shallower grooves maintain better thermal conduction pathways. This spatially varying groove depth allows simultaneous optimization of both alignment and thermal performance.
Solution Approach 2:
The circumferential grooves break the rotational symmetry of the pivot pin by having different depths at different angular positions. This asymmetric groove configuration allows the pivot pin to have different flexibility characteristics in different directions, enabling optimal performance for both alignment compensation and heat dissipation without requiring uniform groove geometry.
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 solution effectively reduces misalignment and temperature-related issues, enhancing the reliability and efficiency of the bearing while maintaining alignment quality and promoting heat dissipation.
Implementation Method 1
providing flexibility to the pivot pin, which radially separate two axially opposed lateral end portions of the central shank, from two cantilevered lateral portions of the pivot pin
Implementation Method 2
increase the conduction and thus reduce the temperature of the active zone
Data Source
AI summary
The invention relates to a pivot pin (5) for an epicyclic gear train sliding bearing, having axially opposed, laterally open circumferential grooves (25a) providing flexibility to the pivot pin, each groove having a radial width and at least one depth (P). At least one of the circumferential grooves (25a,25b) has a said width and/or depth (P) which varies circumferentially.