Segmented Thrust Foil Bearing for Radial Rigidity and Taper Control
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Solution Overview
Problem
In thrust foil bearings, the radial bending of top foils on the downstream side leads to reduced load capacity due to increased pressure and difficulty in forming appropriate taper angles, necessitating a balance between radial rigidity and circumferential flexibility.
Innovation Solution
The design incorporates a bent portion on the downstream end of the top foil, which increases its rigidity against radial bending, and a bump foil structure that supports the top foil with a trapezoidal shape and corrugated configuration to manage pressure distribution and maintain non-contact with the thrust collar under high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the top foil is made thick, then bending in the radial direction is reduced, but inclination deformation in the circumferential direction is hindered, making it difficult to form an appropriate taper angle and decreasing bearing load capacity
Solution Approach 1:
The top foil is divided into multiple top foil pieces arranged in the circumferential direction, with gaps between them. This segmentation allows each piece to independently deform radially while the overall structure maintains circumferential flexibility through the gaps, resolving the contradiction between radial strength and circumferential flexibility.
Solution Approach 2:
The top foil pieces are designed with different local properties: they have sufficient thickness and rigidity in the radial direction to resist bending under fluid pressure, while the gaps between pieces provide the necessary circumferential flexibility. This local differentiation allows each region to optimize for its specific functional requirement.
2Ease of operation
If the top foil is made thin, then circumferential flexibility is improved, but bending in the radial direction increases on the downstream end side, widening the interval between the top foil and thrust collar and decreasing load capacity
Solution Approach 1:
By segmenting the top foil into multiple pieces with gaps between them, the structure achieves both thin-foil circumferential flexibility and adequate radial strength. Each thin piece can flex circumferentially while the segmented configuration prevents excessive radial bending through distributed support.
Solution Approach 2:
The solution moves from considering only foil thickness (one-dimensional property) to incorporating the circumferential arrangement of multiple pieces with gaps (two-dimensional configuration). This dimensional shift allows simultaneous achievement of radial strength and circumferential flexibility through spatial distribution rather than material thickness alone.
3Strength
If the top foil is made thicker, then rigidity against radial bending is increased, but the bearing load capacity decreases due to hindered inclination deformation and difficulty in forming appropriate taper angle
Solution Approach 1:
The top foil is segmented into multiple pieces with gaps, allowing each piece to maintain adequate radial rigidity while the gaps enable collective circumferential deformation. This segmentation allows the formation of appropriate taper angles across the bearing surface, maintaining high load capacity without requiring excessive thickness in individual pieces.
Solution Approach 2:
Different regions of the top foil structure are optimized for different functions: individual pieces have local rigidity for radial load support, while the gap regions provide local flexibility for circumferential adaptation and taper formation. This local quality differentiation resolves the contradiction between radial rigidity and overall load capacity.
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, enhances the load-carrying capacity, and improves the cooling effect by directing lubricant flow, maintaining efficient fluid lubrication even under high loads.
Implementation Method 1
air is introduced between the top foil pieces and the thrust collar by the rotation of the thrust collar. The air forms a wedge-shaped fluid lubricating film between the top foil pieces and the thrust collar, and a load capacity of the thrust foil bearing is exhibited.
Implementation Method 2
The top foil piece (11) has a bent portion (13) on a downstream end side in the rotation direction of the rotation shaft (1). The top foil (10) has rigidity (anisotropic rigidity) that is strong against bending in the radial direction and is flexible in the circumferential direction.
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
A thrust foil bearing (3) of this disclosure includes a base plate (30) provided with an insertion hole through which a rotation shaft is inserted; a corrugated bump foil (20) placed around the insertion hole and supported by the base plate (30); and a top foil (10) which is supported by the bump foil (20), and in which one side in a circumferential direction of the insertion hole is attached to the base plate (30) and the other side in the circumferential direction of the insertion hole is a free end, the thrust foil bearing (3) in which a bent portion (13) which is bent toward the base plate (30) is formed on the other side of the top foil (10) in the circumferential direction.