Journal Bearing Retainer Backup Support for Tab Stress
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Solution Overview
Problem
Foil journal bearings experience high circumferential forces during overload conditions, leading to permanent distortion of the top foil retaining tabs, which affects bearing performance and shortens its lifespan due to excessive bending moment and stress.
Innovation Solution
The design incorporates a backup support structure within the retainer member, where the top foil trailing and leading edge tabs are positioned in slots that allow for increased contact pressure with the backup support during rotation, minimizing bending moment and stress by distributing the force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the top foil retaining tabs are designed to be simple and flexible for ease of manufacture and assembly, then the manufacturing cost and assembly complexity are reduced, but the bearing experiences high bending moment and stress during overload conditions leading to permanent distortion and shortened lifespan
Solution Approach 1:
The top foil is divided into multiple segments with individual retaining tabs, allowing each tab to be independently supported by the backup structure. This segmentation enables the simple flexible tab design to work in conjunction with the backup support structure to resist bending stresses during overload conditions without requiring complex integrated designs
Solution Approach 2:
The backup support structure acts as an intermediary element between the retaining tabs and the retainer member. It provides additional support to the tabs during overload conditions, distributing the bending moment and stress away from the tabs while maintaining the simplicity of the tab design itself
2Reliability
If the retaining design is strengthened to prevent permanent distortion of tabs during overload, then bearing lifespan and performance are maintained, but the device complexity and manufacturing cost increase
Solution Approach 1:
The backup support structure is integrated with the retainer member as a single unified component. This merging eliminates the need for separate backup support elements, reducing assembly steps and device complexity while still providing the necessary support to maintain tab integrity and bearing reliability during overload conditions
3Adaptability or versatility
If the top foil tabs are allowed to have high flexibility for compliant operation, then the foil can yield to pressurized fluid film, but the tabs experience excessive bending moment during overload leading to permanent distortion
Solution Approach 1:
The backup support structure provides localized support specifically at the tab regions where bending moments occur during overload. This local reinforcement allows the rest of the top foil to maintain its compliance and flexibility for yielding to the pressurized fluid film, while only the critical tab areas gain enhanced stress resistance
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 bearing's strength by reducing bending stress and extending its lifespan by ensuring that only the opposite end of the tab is urged into increased contact with the backup support, thereby minimizing metal stress and maintaining performance.
Implementation Method 1
Rotation of the shaft within the retaining member may form and maintain a pressurized fluid film between the shaft and the compliant foil. High speed rotation of the shaft may generate a high pressure in the fluid film and this pressurized fluid film may support the load imposed by the shaft.
Implementation Method 2
whereupon, during rotation of the rotatable member, the trailing edge tab is urged into increased contact, at a subsequent contact pressure higher than the initial contact pressure, with the backup support
Data Source
AI summary
A journal foil bearing includes a bearing retainer having one slot configured to receive a top foil leading edge tab and another slot configured to receive a top foil trailing edge tab. A backup support structure, integral to the bearing retainer, extends between and is at least partially defined by the slots. The retainer is configured so that, during operation, the trailing edge tab further contacts, at an increased contact pressure, the support structure at a position close to the friction force, thereby minimizing top foil bending stress and improving bearing strength.