Thrust Foil Bearing Expansion Geometry for Radial Bending Control
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Solution Overview
Problem
In thrust foil bearings, the radial bending of the top foil on the downstream side is significant due to high fluid pressure, leading to reduced load capacity and difficulty in maintaining an appropriate taper angle, as the foil requires anisotropic rigidity for effective bending and tilt deformation.
Innovation Solution
The thrust foil bearing incorporates an expansion portion on the top foil piece that elongates towards the downstream side, increasing radial bending rigidity and maintaining a strong fluid lubricating film, while allowing efficient fluid flow and cooling, thereby suppressing radial bending and enhancing load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the top foil is thickened to reduce radial bending, then the bending in radial direction is reduced, but the tilt deformation in circumferential direction is hindered
Solution Approach 1:
The top foil is designed with non-uniform thickness distribution, being thicker at the downstream end and thinner at the upstream end. This local variation in thickness provides different mechanical properties at different locations: the thicker downstream portion resists radial bending under high fluid pressure, while the thinner upstream portion allows necessary tilt deformation for maintaining the wedge-shaped lubricating film.
Solution Approach 2:
The thickness parameter of the top foil is changed along its length to achieve anisotropic rigidity. By varying the thickness from upstream to downstream, the foil gains different stiffness characteristics in different regions, enabling it to simultaneously satisfy the conflicting requirements of radial bending resistance and tilt deformation capability.
2Strength
If the top foil is thickened to increase rigidity, then the radial bending is suppressed, but the bearing load capacity decreases due to hindered tilt deformation
Solution Approach 1:
The non-uniform thickness distribution creates local quality variations that optimize performance: the thicker downstream region suppresses radial bending to maintain film strength under high pressure, while the thinner upstream region preserves flexibility for tilt deformation necessary for load-bearing capability through wedge-shaped film formation.
Solution Approach 2:
By changing the thickness parameter along the length of the top foil, the design achieves optimal balance between radial bending suppression and load capacity maintenance. The gradient thickness profile allows the foil to exhibit appropriate rigidity where needed while maintaining flexibility where deformation is required for load support.
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 effectively suppresses radial bending of the top foil on the downstream side, maintaining a strong fluid lubricating film and improving the bearing's load capacity by increasing the rigidity against radial bending and facilitating efficient cooling.
Implementation Method 1
air is introduced between the top foil pieces and the thrust collar due to rotation of the thrust collar. This air forms a wedge-shaped fluid lubricating film between the top foil piece and the thrust collar, and the thrust foil bearing exhibits a load capacity
Implementation Method 2
This air forms a wedge-shaped fluid lubricating film between the top foil piece and the thrust collar
Implementation Method 3
The thrust foil bearing incorporates an expansion portion on the top foil piece that elongates towards the downstream side, increasing radial bending rigidity and maintaining a strong fluid lubricating film
Implementation Method 4
air is introduced between the top foil pieces and the thrust collar due to rotation of the thrust collar
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A thrust foil bearing (3) of the present disclosure includes a base plate (30) which includes an insertion hole (30a) through which a rotation shaft (1) is inserted, a back foil (20) which is disposed around the insertion hole (30a) and supported by the base plate (30), and a top foil (10) which is supported by the back foil (20), wherein the top foil (10) includes an expansion portion (13) in which a width of the expansion portion in a virtual straight line direction in which a virtual straight line extends decreases in a direction orthogonal to the virtual straight line, the virtual straight line being supported by the back foil (10) on a most downstream side in a rotation direction of the shaft.