Journal Bearing Retainer Backup Support for Stress Reduction
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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 compromises bearing performance and shortens its lifespan due to excessive bending moment and stress.
Innovation Solution
A backup support structure integral to the retainer member, positioned between the top foil trailing edge tab slot and the top foil leading edge tab slot, minimizes bending moment and stress by urging the top foil into contact with the backup support during rotation, thereby reducing metal stress and enhancing bearing strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the top foil retaining tab is designed to be simple and flexible for ease of installation, then the manufacturing cost is minimized and installation is easier, but the tab experiences high bending moment and stress during overload conditions leading to permanent distortion and shortened bearing life
Solution Approach 1:
The retaining system is segmented into multiple functional zones: the top foil retaining tab for simple attachment, the backup support structure for strength, and the circumferential force transfer mechanism for load distribution. This segmentation allows each component to be optimized for its specific function while working together to solve the overall contradiction between simplicity and strength.
Solution Approach 2:
The backup support structure provides excessive support capacity beyond what the simple retaining tab can handle. During normal operation, the simple tab suffices, but during overload conditions, the backup structure activates to prevent permanent distortion, effectively providing more strength than needed for常规 operation but necessary for extreme conditions.
2Ease of manufacture
If the top foil retaining tab is made simple for ease of manufacture, then manufacturing cost is reduced, but the tab cannot withstand high circumferential forces during overload conditions
Solution Approach 1:
The backup support structure acts as an intermediary between the simple retaining tab and the high circumferential forces. It mediates the load transfer, allowing the simple tab to perform its attachment function while the backup structure handles the excessive forces during overload conditions, thus maintaining reliability without complicating the manufacturing of the primary retaining component.
Solution Approach 2:
The backup support structure is positioned in advance to cushion against potential overload conditions. It is pre-configured to engage when circumferential forces exceed normal operating limits, preventing permanent distortion before it occurs and maintaining bearing reliability during extreme events.
3Strength
If a higher strength retaining design is implemented to prevent permanent distortion, then bearing strength and reliability are improved, but the design complexity increases and manufacturing cost rises
Solution Approach 1:
The design applies local quality by concentrating the complex, high-strength backup support structure only in the specific location where circumferential forces are transmitted to the retaining tab. The rest of the bearing system maintains its simple, conventional design. This localized approach provides necessary strength enhancement without requiring complex design throughout the entire bearing assembly.
Solution Approach 2:
The backup support structure is merged with the retainer member as an integral component rather than a separate assembly. This merging simplifies the overall design by eliminating additional fastening requirements and assembly steps, reducing design complexity while maintaining the strength benefits of having both the simple retaining tab and the integrated backup support.
4Ease of operation
If the top foil retaining tab is designed to be simple, then installation and manufacturing are easier, but the bending moment causes permanent distortion under high loads
Solution Approach 1:
The backup support structure is nested within the retainer member geometry, positioned to provide support to the retaining tab without interfering with the simple installation process. The nested configuration allows the simple retaining tab to be installed first, with the backup support structure already in place to prevent distortion under load, maintaining both ease of operation and structural stability.
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 backup support structure effectively reduces bending stress and improves the durability of the foil journal bearing by distributing forces more evenly, thereby extending its operational life and maintaining performance under high loads.
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
A resilient backing member, such as a spring foil, may be disposed between the top foil and the retaining member to accommodate deflections of the foil resulting from pressurization, centrifugal forces and temperature differentials in order to maintain adequate film layer geometry.
Implementation Method 3
A resilient backing member, such as a spring foil, may be disposed between the top foil and the retaining member to accommodate deflections of the foil resulting from pressurization, centrifugal forces and temperature differentials.
Data Source
Figure 1~2
Figure 3
AI summary
A journal foil bearing (130) includes a bearing retainer (138) having one slot (144) configured to receive a top foil leading edge tab (152) and another slot (142) configured to receive a top foil trailing edge tab (150). A backup support structure (146), 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 (150) contacts the support structure at a position close to the friction force, thereby minimizing top foil bending stress and improving bearing strength.