Asymmetric Tolerance Ring for Disk Drive Actuator Vibration
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Solution Overview
Problem
Hard disk drives (HDDs) face performance degradation due to vibrations and tight tolerances, leading to off-track issues and data errors as components shrink and data tracks per inch increase, exacerbated by imbalances and unwanted motion during disk rotation.
Innovation Solution
The use of a tolerance ring with asymmetric chamfers to improve the connection between the pivot shaft and actuator, enhancing rotational stability and reducing vibration modes like the butterfly mode, thereby increasing actuator bandwidth and disk drive performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If components are shrunk and data tracks per inch are increased to improve storage capacity, then data capacity increases, but vibrations and off-track issues worsen leading to data errors
Solution Approach 1:
The patent applies asymmetry by providing a tolerance ring with asymmetric chamfers (first chamfer at 45 degrees, second chamfer at 15 degrees) that creates uneven contact surfaces. This asymmetric geometry is specifically designed to reduce unwanted motion modes, particularly the butterfly mode, thereby reducing vibrations and improving head positioning accuracy on high-density tracks while maintaining the high data capacity enabled by component shrinkage
2Measurement precision
If tolerance between pivot shaft and actuator is reduced to improve positioning precision, then positioning accuracy improves, but manufacturing complexity and cost increase
Solution Approach 1:
The tolerance ring serves as an intermediary component between the pivot shaft and the actuator. It provides a compliant connection that absorbs tolerance variations through its elastic material properties and asymmetric chamfer geometry, achieving stable head positioning without requiring extremely tight manufacturing tolerances on the pivot shaft or actuator components themselves
Solution Approach 2:
The patent changes the geometric parameters of the tolerance ring by introducing asymmetric chamfers with specific angles (45 degrees and 15 degrees). This parameter change optimizes the contact mechanics between components, reducing unwanted motion and improving positioning accuracy while maintaining manufacturability through standardized angular values
3Speed
If actuator bandwidth is increased to improve positioning speed, then positioning speed increases, but vibrations and unwanted motion increase
Solution Approach 1:
The asymmetric chamfer design (45 degree first chamfer, 15 degree second chamfer) creates a compliant connection that selectively dampens unwanted vibration modes, particularly the butterfly mode, while allowing the actuator to operate at higher bandwidths for faster positioning. The asymmetry provides directional compliance that reduces harmful vibrations without sacrificing positioning speed
Data Source
AI summary
Described herein is a tolerance ring for a disk drive that includes a substantially cylindrical body having outer surface. The tolerance ring can be positioned between a rotational bearing and an actuator for providing rotational movement of the actuator. The tolerance ring can also include a contact member, positioned along the outer surface, that protrudes outward from the outer surface. The contact member can be connected to the outer surface by first and second angulated arms that extend from the outer surface to the contact member at different angles relative to the outer surface.