Accessory Gearbox Single Roller Bearing Load Absorption
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Solution Overview
Problem
Existing gas turbine engine accessory gearboxes require significant space due to the need for minimum separation between roller bearings to accommodate misalignment, limiting the reduction of gearbox thickness and increasing the space requirement.
Innovation Solution
The use of a single roller bearing with a double row of oblique-contact balls or rollers, where the fixed inner race is mounted on a shaft secured to the housing, allowing the gearbox to absorb radial, axial, and bending loads, enabling more compact gear mounting and reduced axial clearances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional roller bearings are used with minimum space between axes to accommodate misalignment, then the gearbox can function correctly, but the thickness and space requirements increase
Solution Approach 1:
The patent merges multiple bearing functions into a single roller bearing unit. The bearing simultaneously supports radial loads, axial loads, and bending moments, eliminating the need for separate bearings and reducing the minimum distance between axes. This consolidation allows the gear wheel to be supported by one bearing instead of two, directly reducing gearbox thickness.
Solution Approach 2:
The roller bearing is designed with multi-functionality to handle various types of loads (radial, axial, and bending moments) that were previously required separate bearing arrangements. The bearing's raceways and contact angles are configured to provide universal support for misalignment and different load directions, making a single bearing sufficient for what previously required multiple bearings.
2Volume of stationary object
If the minimum distance between axes is reduced for compact mounting, then space requirements decrease, but the capacity for misalignment of rollers is reduced
Solution Approach 1:
The patent changes the geometric parameters of the roller bearing, specifically the contact angles and raceway configurations. By optimizing these parameters, the bearing maintains its misalignment capacity even when the distance between axes is reduced. The oblique-contact design allows the bearing to accommodate angular deviations while occupying less space.
3Length of stationary object
If a single roller bearing is used to support a gear wheel, then the gearbox thickness is reduced, but the bearing must absorb complex loads including bending moments and axial forces
Solution Approach 1:
The bearing design incorporates dynamic characteristics through its oblique-contact geometry, allowing it to adapt to varying load conditions. The contact angles are designed to distribute complex loads (radial, axial, and bending moments) across the roller-bore interface dynamically, maintaining strength while enabling compact mounting.
Data Source
AI summary
An accessory gearbox capable of driving the accessory devices of a gas turbine engine, such as an aircraft engine. Said accessory gearbox includes a housing and a plurality of gear wheels having axes that are parallel to one another inside the housing. The housing includes a means for attaching the accessory devices to the wall of the housing and driving them, via the gear wheels, through openings in the wall of the housing. The gear wheels are supported in the housing by rolling-element bearings. Each rolling element includes a first ring that is stationary relative to the housing, and a movable ring, secured to the gear wheel, wherein at least one of said gear wheels is supported by a single rolling element.