Aircraft Transmission Bearings With Elastic Preload for Thermal Stability
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Solution Overview
Problem
Aircraft using hybrid rolling bearings face issues due to differing coefficients of thermal expansion between rolling elements and rings, leading to performance deterioration and stability loss from varying operating temperatures and lubrication problems, necessitating a solution that maintains stability across temperature changes and load variations.
Innovation Solution
The implementation of a transmission system with preloaded elastic members and hybrid bearings where outer rings float axially in response to loads, and inner rings are axially preloaded to maintain consistent clearance and stability, using materials with different thermal expansion coefficients for the rings and rolling elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If hybrid rolling bearings are used in the transmission system, then the transmission offers reduced weight and superior dynamic behavior, but the assembly clearances between the rings and rolling elements increase significantly when operating temperature rises due to different coefficients of thermal expansion
Solution Approach 1:
The invention introduces an axial play between the inner ring and the shaft, transforming the rigid connection into a flexible one. This parameter change allows the inner ring to move axially in response to thermal expansion differences, compensating for clearance variations and maintaining stable bearing performance across temperature ranges.
Solution Approach 2:
The invention transitions from a static, fixed-position inner ring to a dynamic system where the inner ring can move axially along the shaft. This dynamic adjustment capability enables the bearing to adapt to thermal expansion changes, maintaining optimal clearance conditions despite temperature variations.
2Temperature
If the operating temperature rises, then the rings expand more than the rolling elements causing increased assembly clearances, but this results in considerable deterioration in the performance and stability of the rolling bearings
Solution Approach 1:
The invention changes the positional parameter of the inner ring from fixed to variable, introducing axial play that allows the inner ring to shift position in response to thermal expansion. This parameter change enables the bearing to maintain reliable performance across a broad temperature range by compensating for clearance variations.
3Temperature
If the operating temperature lowers significantly, then the rings contract more than the rolling elements, but this results in overloading of the rings and the rolling elements
Solution Approach 1:
The dynamic axial movement capability of the inner ring allows it to adjust its position based on temperature conditions. During cooling, the inner ring moves to accommodate contraction, preventing excessive loading of the rings and rolling elements, thereby preserving bearing strength and load capacity across temperature cycles.
4Temperature
If the transmission is subject to considerable thermal gradients with different temperature conditions for inner and outer rings, then the assembly clearances vary causing overloading or loss of stability of the rolling bearings
Solution Approach 1:
The invention introduces axial play as a parameter change that allows the inner ring to independently adjust its axial position. This enables the bearing to compensate for differential thermal expansion between the inner and outer rings, maintaining stable clearances and preventing overloading or instability under thermal gradient conditions.
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 ensures robust and precise axial preload, maintaining transmission stability across a broad temperature range and reducing the risk of overloading and fatigue, while minimizing axial play and vibrations, thus enhancing the aircraft's operational efficiency and reliability.
Implementation Method 1
a plurality of elastic members arranged between the input shaft and the outer rings, and configured to act axially on the inner rings
Implementation Method 2
The rolling bearings offer the relative transmission shaft both an axial and a radial support
Implementation Method 3
the different coefficient of thermal expansion between the material of the rolling bodies and that of the rings
Data Source
AI summary
An aircraft is described comprising: a support element; a shaft rotating about an axis; a pair of oblique rolling bearings mounted so as to couple the shaft to the support element rotatingly about the axis; the rolling bearings comprising: respective first races cooperating radially in contact with a first component defined by one from the support element and the shaft; respective second races cooperating radially in contact with a second component defined by the other from the support element and the shaft; and respective pluralities of rolling elements adapted to roll on the first and second races; the aircraft further comprises a pair of preloaded elastic members, which couple the first races to the first component respectively, axially and in an elastically yielding manner.