HDD Pivot Bearing Shield Cap Stepped Surface Particle Control
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Solution Overview
Problem
Existing pivot bearing units in hard disk drives face challenges in reducing outparticles due to air flow through the bearings, with conventional shield caps and flange configurations allowing large gaps that allow air and particles to escape, limiting the effectiveness of particle capture.
Innovation Solution
A pivot bearing unit design featuring a shield cap with a stepped axial inner surface and a flange portion with inclined surfaces, forming a longer labyrinthine gap to reduce air flow and particle discharge, with specific gap dimensions optimized to minimize particle escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional shield caps and flange configurations are used, then the structure is simple and easy to manufacture, but large gaps allow air flow and particle discharge
Solution Approach 1:
The shield cap is divided into multiple functional surfaces: a first cap flat surface facing the bearing, a second cap flat surface parallel to the first, and a cap rising surface connecting them. This segmentation creates multiple gap regions (first gap between first cap flat surface and shield member, second gap between second cap flat surface and outer ring) that collectively form a labyrinthine structure to block particle discharge while maintaining manufacturing feasibility.
Solution Approach 2:
The invention transitions from a conventional single-flat-surface shield cap to a multi-level stepped structure with surfaces at different axial positions. The cap rising surface introduces an axial dimension variation, creating a three-dimensional labyrinthine gap structure that effectively blocks particle discharge paths without significantly increasing radial or lateral dimensions.
2Object-affected harmful factors
If the shield cap is positioned closer to the bearing to reduce gaps, then particle capture improves, but manufacturing precision requirements increase
Solution Approach 1:
Instead of reducing a single large gap to a very small dimension (which would require high precision), the invention segments the gap into multiple smaller gaps (first gap and second gap) separated by the cap rising surface. Each individual gap can be manufactured within standard tolerances, while their combined labyrinthine effect achieves superior particle blocking performance.
Solution Approach 2:
Different surfaces of the shield cap have different functions: the first cap flat surface creates a narrow first gap for effective particle blocking near the bearing, the second cap flat surface creates a larger second gap that is still effective due to the labyrinthine configuration, and the cap rising surface connects these regions. This local differentiation of gap sizes allows each region to be manufactured within achievable precision while collectively achieving superior particle capture.
3Object-affected harmful factors
If air flow through bearings is reduced to capture particles, then particle discharge decreases, but air flow needed for cooling and operation is restricted
Solution Approach 1:
The shield cap acts as an intermediary structure between the bearing interior and the HDD interior. It creates a controlled transition zone with labyrinthine gaps that selectively restrict particle-laden air flow while allowing sufficient air passage for thermal management. The multi-surface configuration provides turbulence and flow path complexity that enhances particle capture without completely blocking air flow.
Solution Approach 2:
The cap rising surface introduces axial dimension variation to the gap structure, creating a three-dimensional flow path that increases air flow resistance for particles while maintaining sufficient cross-sectional area for air passage. The stepped configuration forces air to navigate multiple levels, enhancing particle deposition opportunities without completely restricting volumetric air flow.
Data Source
AI summary
In an HDD actuator pivot bearing unit 10, an axial inner surface 22a of a shield cap 22 is formed into a stepped shape so that an axial minimum gap a1 with a shield member 14e of one bearing 14 is narrower than an axial minimum gap a2 with an outer ring 14b and so that an axial minimum gap a3 with a boundary position 14b3 between an axial end face of the outer ring 14 and an annular groove 14b1 is narrower than the axial minimum gap a2 with the outer ring 14. By doing so, the amount of air passing through an interior of the bearing can be reduced to thereby reduce outparticles.