Multi-Arc Foil Bearing Design for Vibration Damping
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Solution Overview
Problem
Foil bearings for high-speed, high-temperature applications like gas turbines and turbochargers face challenges in manufacturing cost and assembly time due to the need for multiple components, and they often reduce bearing surface areas, compromising supportability and vibration damping.
Innovation Solution
A multi-arc foil bearing design where the circumferential end portions of foils intersect and are held by the outer member's inner surface, eliminating the need for separate elastic members and allowing continuous coverage of the outer member's surface, with sliding end portions generating friction to damp vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If separate elastic members (back foils) are used to support the top foil, then the foil bearing can elastically support loads, but the manufacturing cost and assembly time increase
Solution Approach 1:
The patent merges the back foil and top foil into a single integrated foil structure. The foil includes a back portion and a top portion that are continuously connected, eliminating the need for separate elastic members. This integration maintains the elastic load support capability while reducing the number of components and simplifying assembly.
Solution Approach 2:
The integrated foil structure performs multiple functions simultaneously: the back portion provides elastic support, the top portion forms the bearing surface, and the continuous connection between them provides both structural integrity and load distribution. This multi-functionality eliminates the need for separate specialized components.
2Strength
If multiple separate components are used in the foil bearing, then elastic support is achieved, but the bearing surface area is reduced
Solution Approach 1:
By merging the back foil and top foil into a single continuous structure, the patent eliminates the gaps and interface regions that would exist between separate components. This allows the bearing surface to extend continuously across the entire inner circumferential surface of the outer member, maximizing the bearing surface area.
3Device complexity
If rigid bearing surfaces are used in air dynamic pressure bearings, then the structure is simple, but radial bearing gaps are difficult to manage under temperature changes
Solution Approach 1:
The patent employs a flexible foil structure that can dynamically adapt to temperature changes and shaft rotation. The foil's flexibility allows it to maintain appropriate radial bearing gaps automatically as conditions change, eliminating the need for precise pre-management of gaps that rigid structures require.
Solution Approach 2:
The foil's physical properties (flexibility and elasticity) enable it to change its shape and position in response to varying operating conditions such as temperature and load. This parameter adaptation allows the bearing to maintain optimal performance across different operating states without complex adjustment mechanisms.
4Stability of the object's composition
If the circumferential ends of foils are fixed to the outer member, then the foils are held in position, but the bearing surface area is reduced by the fixing structures
Solution Approach 1:
The patent nests the foil holding portions within grooves formed in the outer member's inner circumferential surface. This nesting arrangement allows the foils to be securely held in position while minimizing the space occupied by the fixing structures, thereby preserving maximum bearing surface area.
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 design reduces manufacturing costs and assembly time, maintains bearing surface areas, and enhances vibration damping, enabling stable support under high-speed, high-temperature conditions.
Implementation Method 1
during rotation of the shaft, an air film is formed between an outer circumferential surface of the shaft and an inner circumferential surface of the top foil. With this, the shaft is supported in a non-contact manner
Implementation Method 2
a spring-like member called a back foil is arranged on a radially outer side thereof. With this, a load on the top foil is elastically supported by the back foil
Implementation Method 3
When at least one of the end portions in the circumferential direction of each of the plurality of foils is slidable against the outer member, frictional energy is generated by sliding between the plurality of foils and the outer member. With this, vibration to be cause by relative rotation of the shaft can be damped
Data Source
Figure 1~2
Figure 3~4b
Figure 5~6
AI summary
A foil bearing includes an outer member (11), and a plurality of foils (13) that are mounted to an inner circumferential surface (11a) of the outer member (11) and directly face the inner circumferential surface (11a) of the outer member (11) in a radial direction. The foils (13) each include holding portions (13a, 13b) that are formed at both circumferential ends and held while in contact with the outer member (11) and a body portion (13c) having a bearing surface (A) formed circumferentially between the holding portions (13a, 13b). At least one end portion in a circumferential direction of the body portion (13c) is raised radially inward with respect to the inner circumferential surface (11a) of the outer member (11). The end portions of the body portion (13c) intersect each other in an axial view.