Fluid Dynamic Bearing Recirculation Channel and Sealing Gap Design
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Solution Overview
Problem
Fluid dynamic bearing systems, particularly those open at both ends, face issues with air bubbles accumulating due to centrifugal effects and pressure gradients, leading to impaired functionality and potential breakdown, as well as challenges in maintaining pressure equilibrium and fluid retention.
Innovation Solution
A fluid dynamic bearing system design with a recirculation channel having a larger radial diameter than the sealing gap, and a sealing gap that is tapered and inclined, allowing air bubbles to be directed outwards and ensuring improved pressure equilibrium and fluid retention through centrifugal forces and fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bearing gap is sealed using capillary seals with tapered expansion, then the sealing effect and fluid retention are improved, but air bubbles accumulate in the transition regions and impair bearing function
Solution Approach 1:
The patent extracts the harmful air bubbles from the bearing system by providing dedicated air removal channels that transport air bubbles away from the critical bearing gap regions. The air bubbles are separated from the bearing fluid and removed through specific pathways that do not interfere with the sealing function of the capillary seals.
Solution Approach 2:
The patent introduces intermediary air removal channels and air vents that act as mediators between the bearing gap and the external environment. These intermediary structures allow air bubbles to be transported out of the bearing system without compromising the sealing effect of the capillary seals in the bearing gap.
2Productivity
If the recirculation channel has steps or edges for fluid flow, then the bearing fluid circulation is maintained, but air bubbles accumulate at transition regions and may lead to bearing breakdown
Solution Approach 1:
The patent segments the recirculation channel into distinct functional regions: a bearing fluid circulation path and a separate air removal path. By dividing the channel into these segments with different purposes, the system maintains efficient fluid circulation while providing dedicated pathways for air bubble removal, preventing accumulation at transition regions.
Solution Approach 2:
The patent adds a new dimensional aspect to the recirculation channel design by incorporating vertical air vents and upwardly opening channels. This dimensional change allows air bubbles to be removed in a direction perpendicular to the main fluid flow, creating separate pathways that eliminate air accumulation problems at horizontal transition regions.
3Stress or pressure
If bearing fluid is pumped inwards by axial bearings, then the bearing gap is pressurized, but air bubbles migrate inwards due to pressure gradients and accumulate at certain points
Solution Approach 1:
The patent employs asymmetric design in the air removal channels, with channels having different orientations and opening directions at various locations around the bearing. This asymmetry creates favorable pressure gradients that guide air bubbles toward removal outlets while maintaining the necessary inward pressure for bearing operation. The asymmetric configuration ensures air bubbles are directed outward against the inward fluid flow pressure.
Solution Approach 2:
The patent inverts the conventional approach by providing air removal channels that open in upward directions opposite to the downward inward fluid flow. This inversion allows air bubbles, which naturally rise, to be removed in the opposite direction to the main fluid pressure gradient, preventing air migration inward while maintaining bearing gap pressurization.
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
Effectively eliminates air bubbles and maintains pressure equilibrium, preventing bearing failure and improving the operational reliability of fluid dynamic bearing systems.
Implementation Method 1
allowing air bubbles to be directed outwards and ensuring improved pressure equilibrium and fluid retention through centrifugal forces and fluid flow
Implementation Method 2
One widespread method of sealing the bearing gap is the use of gap seals, particularly capillary seals, which exploit the material-specific properties of the bearing fluid, i.e. the active principles behind capillary, adhesive and cohesive forces
Implementation Method 3
The bearing fluid covers the surfaces of the thrust plates and the hub thereby forming a meniscus having a concave surface at the contact surface to the air. This goes to increase the retaining power of the bearing fluid, particularly when subject to shock
Data Source
AI summary
The invention relates to a fluid dynamic bearing system that comprises at least one stationary part that has a shaft and two bearing plates disposed on the shaft at a mutual spacing, and at least one rotating part that is supported so as to rotate about a rotational axis with respect to the stationary part, and comprises a bearing bush and a sleeve enclosing the bearing bush. A bearing gap filled with bearing fluid is provided between the parts and at least one sealing gap for sealing the bearing gap that extends concentric to the rotational axis. The bearing comprises at least one fluid dynamic radial bearing and two fluid dynamic axial bearings and at least one recirculation channel that connects the two axial bearing regions to each other. According to the invention, the largest radial diameter of the recirculation channel is greater than or equal to the largest diameter of the sealing gap, and the smallest radial diameter of the recirculation channel is greater than or equal to the largest diameter of an adjacent bearing plate. Moreover, additional and effective deairing of the recirculation channel is effected by a venting device. To realize improved equilibrium of pressure in the bearing gap and improved retention of the bearing fluid, the sealing gaps can be inclined, at least in sections, at an angle α, β with respect to the rotational axis, wherein the angles may have different sizes.