Thrust Foil Bearing Overlap Geometry for Higher Gas Load Capacity
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Solution Overview
Problem
Thrust foil bearings using gas as lubricants have a lower load capacity compared to those using oil due to the smaller floating gap, which limits their application, and reducing this gap is challenging without increasing rigidity and causing contact with the thrust collar.
Innovation Solution
The thrust foil bearing design features foils with a smaller angle at the radially inner end of the overlapping portion compared to the radially outer end, reducing the rigidity difference and allowing for a smaller floating gap, enabling equal bending of the foils and increased load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the floating gap is reduced to increase load capacity, then the load capacity is improved, but the foil rigidity increases causing contact with the thrust collar
Solution Approach 1:
The foil is designed with non-uniform rigidity distribution through varying the circumferential angles at radial ends. The radially outer end has a larger circumferential angle providing greater rigidity to prevent contact with the thrust collar, while the radially inner end has a smaller circumferential angle allowing sufficient bending. This local differentiation of rigidity properties enables the foil to maintain appropriate flexibility for load bearing while preventing contact at critical regions.
Solution Approach 2:
The foil structure employs asymmetric angle configuration where the circumferential angles at the radial ends are deliberately made different. This asymmetric design creates a non-uniform rigidity distribution that is optimized for the specific loading and geometric conditions of the thrust foil bearing, allowing the foil to bend appropriately without contacting the thrust collar even at reduced floating gaps.
2Use of energy by moving object
If gas is used as lubricant to reduce torque, then the torque is reduced, but the load capacity decreases due to smaller floating gap
Solution Approach 1:
The invention changes the geometric parameters of the foil, specifically the circumferential angles at radial ends, to optimize the floating gap configuration. By adjusting these angles, the foil achieves optimal bending characteristics that maximize load capacity while maintaining the benefits of gas lubrication with minimal torque.
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 effectively increases the load capacity of the thrust foil bearing by reducing the floating gap, preventing contact with the thrust collar and maintaining stable operation under high temperature and high-speed conditions.
Implementation Method 1
a foil material 130 having a hollow disc shape is divided at a plurality of positions in a circumferential direction, and an entire region of the foil material 130 in the circumferential direction is used as the foils 122
Implementation Method 2
Lubricants to be used in the foil bearing is gas (air), and hence the foil bearing has an advantage of having lower torque than that of a fluid dynamic bearing that uses oil as the lubricants
Implementation Method 3
When the lubricants (air) are pushed into a small gap portion of the wedge-shaped bearing gap C′, the pressure of the lubricants are increased. With this pressure, the thrust collar 106 is supported in a non-contact manner
Data Source
AI summary
Each of foils (22) includes: a top foil portion (22a) including a bearing surface (S); and a back foil portion (22b), which is formed on an upstream side of the top foil portion (22a), and is arranged so as to overlap behind the top foil portion (22a) of the adjacent foil (22) (on a side opposite to the bearing surface (S)). An angle (E) covering a radially inner end of an overlapping portion (P) between the adjacent foils (22) is smaller than an angle (D) covering a radially outer end of the overlapping portion (P).