Variable-Stiffness Air Bearing for Stable High-Speed Shaft Support
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Solution Overview
Problem
Existing air bearings for compressors in fuel cell systems face challenges in optimally distributing stiffness along the circumference, leading to instability and wear issues during high-speed rotation of the shaft.
Innovation Solution
The air bearing design incorporates a spring foil with varying spring stiffness areas, including embossed beads for higher stiffness and tapering points for lower stiffness, along with elastically deformable elements, to create a stable and robust bearing unit that can efficiently guide and support the rotating shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spring foil has uniform stiffness, then the structure is simple to manufacture, but the shaft rotation becomes unstable and wear occurs during high-speed rotation
Solution Approach 1:
The spring foil is designed with varying wall thicknesses to create different stiffness characteristics in different circumferential regions. First material regions have greater wall thickness for higher stiffness, while second material regions have reduced wall thickness at tapered sections for lower stiffness. This local variation in quality allows optimal distribution of stiffness around the circumference, improving shaft rotation stability without requiring a completely complex structure.
Solution Approach 2:
The spring foil's base body is divided into multiple material regions with different stiffness characteristics. The first material regions with higher stiffness and second material regions with lower stiffness are arranged circumferentially offset from each other. This segmentation allows each region to perform its specific function, creating a balanced stiffness distribution that prevents shaft instability during high-speed rotation.
2Reliability
If the wall thickness is reduced at tapered sections, then the spring stiffness is lowered for better stability, but the structural strength is reduced
Solution Approach 1:
The base body is designed with non-uniform wall thickness, creating regions of different mechanical properties. The tapered sections with reduced wall thickness provide lower stiffness for stability, while other sections maintain greater thickness for strength. This local differentiation allows the structure to achieve both stability and adequate strength without compromising either property throughout the entire component.
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 optimally distributes stiffness, allowing the shaft to rotate stably and robustly at high speeds without wear, facilitating the manufacture of a reliable compressor for fuel cell systems.
Implementation Method 1
A spring foil, which is elastically deformable, is arranged in the opening and comprises a top foil also located in the opening, with the spring foil positioned between the outer ring and the top foil
Data Source
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AI summary
The invention relates to an air bearing (32), particularly for a bearing unit (30) of a compressor (28), comprising an outer ring (10), which surrounds a central opening (22) for receiving a shaft (13), a spring film (11) arranged in the opening (22), said spring film being elastically deformable, and a top film (12) arranged in the opening (22), wherein the spring film (11) is arranged between the outer ring (10) and the top film (12). According to the invention, the spring film (11) has an integrally formed main body (34), and the spring film (11) has first material regions (81) having a first spring stiffness and second material regions (82) having a second spring stiffness, wherein each respective first material region (81) is arranged offset to each respective second material region (82) in the circumferential direction (U) of the opening (22), and wherein the first spring stiffness is higher than the second spring stiffness. The invention also relates to a bearing unit (30), which comprises an air bearing (32) according to the invention and a shaft (13), which is rotatably mounted in the opening (22) of the air bearing (32), and a compressor, particularly for a fuel cell system, which comprises a bearing unit (30) according to the invention.