Thrust Foil Bearing Shim Structure for Fluid Film Formation
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Solution Overview
Problem
Existing thrust foil bearings face challenges in forming a desired fluid lubricating film due to the need for precise machining accuracy, which can affect their load capacity.
Innovation Solution
The thrust foil bearing incorporates a base plate with a supporting surface, a step member formed in a stair shape or by overlapping shims, and a back foil supported by both the base plate and the step member, allowing for improved machining accuracy and fluid film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an inclined surface is formed by cutting work on a base plate to create a wedge-shaped gap, then the bearing structure can support load, but machining accuracy must be ensured to form a desired fluid lubricating film
Solution Approach 1:
The inclined surface is segmented into multiple discrete shims with different thicknesses arranged in sequence. Instead of forming a continuous inclined surface through complex cutting work, the bearing structure uses stacked shims (e.g., 104, 105, 106, 107) that create the wedge-shaped gap through their cumulative thickness variation, significantly simplifying manufacturing while maintaining precision
Solution Approach 2:
Shims are introduced as intermediary elements between the base plate and the back foil. These shims act as mediators that establish the required wedge-shaped gap geometry without requiring direct machining of the base plate at high precision, thereby decoupling the manufacturing complexity from the precision requirement
2Reliability
If a wedge-shaped gap is formed to create fluid lubricating film, then load capacity is enabled, but precise machining is required which increases manufacturing difficulty
Solution Approach 1:
The wedge-shaped gap structure is segmented into multiple shims of varying thicknesses rather than requiring a single precisely machined inclined surface. This segmentation allows the fluid lubricating film to be formed through the cumulative effect of discrete shim layers, maintaining reliability while reducing machining requirements
Solution Approach 2:
The shims used to form the wedge-shaped gap can be manufactured as simple, inexpensive components with standard thickness tolerances. Even if individual shims wear or deform, they can be replaced independently without requiring re-machining of the entire base plate, thus maintaining reliable lubricating film formation with ease of manufacture
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 enhances the load capacity of the thrust foil bearing by enabling the formation of a proper fluid lubricating film, even with less stringent machining requirements.
Implementation Method 1
rotation of the thrust collar causes a lubricating fluid to be introduced into a space between the top foil piece and the thrust collar. This lubricating fluid forms a wedge-shaped fluid lubricating film between the top foil piece and the thrust collar, thereby making the load capacity of the thrust foil bearing
Data Source
AI summary
A thrust foil bearing includes: a base plate including an insertion hole through which a shaft is inserted, and a supporting surface expanding in a direction orthogonal to an axial direction of the insertion hole; a step member placed on the supporting surface and formed of a different body from the base plate; and a back foil extending in a circumferential direction of the insertion hole and in which one part of the back foil is supported by the supporting surface and another part of the back foil next to the one part in the circumferential direction is supported by the step member.