Biasing Lead Screw Threads to Eliminate Hysteresis in HDD LUL Ramps
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Solution Overview
Problem
Current hard disk drives with traditional load/unload ramp mechanisms experience lead screw hysteresis, which hampers the responsiveness and efficiency of the ramp assembly's vertical translation, particularly in multi-disk systems with reduced read-write heads, leading to increased costs and complexity.
Innovation Solution
A vertically translating load/unload ramp mechanism is implemented, utilizing a stepper motor-driven lead screw with a biasing member and magnetically engaged guide posts to minimize the gap between the lead screw and ramp assembly threads, thereby reducing or eliminating lead screw hysteresis by maintaining constant engagement throughout the ramp's stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional lead screw mechanism is used for vertical translation of the ramp assembly, then the structure is simple, but lead screw hysteresis occurs which reduces responsiveness and efficiency
Solution Approach 1:
A biasing member is introduced as an intermediary element between the lead screw and ramp assembly. This biasing member applies a constant biasing force that maintains continuous engagement between the lead screw threads and ramp assembly threads, eliminating the gap that causes hysteresis while preserving the simplicity of the lead screw mechanism
Solution Approach 2:
The patent changes the engagement parameter between the lead screw and ramp assembly by applying a constant biasing force. This force modifies the normal force between the threaded surfaces, ensuring continuous contact and eliminating the intermittent engagement that causes hysteresis, thereby improving responsiveness without complicating the mechanism
2Reliability
If the gap between lead screw and ramp assembly threads is reduced, then hysteresis is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The biasing member serves as a mediator that actively maintains the desired gap minimization. Rather than relying on tight manufacturing tolerances to keep the gap small, the biasing member dynamically compensates for variations, ensuring consistent engagement and hysteresis reduction while allowing for more relaxed manufacturing tolerances
3Productivity
If a vertically translating ramp mechanism is implemented, then load/unload efficiency is improved, but lead screw hysteresis increases without biasing
Solution Approach 1:
The biasing member is positioned as an intermediary between the lead screw and ramp assembly, applying a constant biasing force that eliminates the harmful hysteresis effects. This allows the vertically translating mechanism to operate efficiently without the detrimental intermittent engagement that would otherwise occur
Solution Approach 2:
The biasing member applies a preliminary counteracting force that prevents hysteresis from occurring in the first place. By maintaining constant engagement pressure before any reverse motion occurs, the biasing member counteracts the tendency for gap formation and eliminates the root cause of hysteresis, preserving load/unload efficiency
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 solution enhances the responsiveness and efficiency of the ramp assembly's movement, reducing undesirable hysteresis effects and improving the overall performance and cost-effectiveness of the hard disk drive by ensuring consistent engagement between the lead screw and ramp assembly threads.
Implementation Method 1
magnetically engaged guide posts to minimize the gap between the lead screw and ramp assembly threads
Data Source
AI summary
An approach to a reduced-head hard disk drive (HDD) includes a load/unload (LUL) ramp subsystem that includes a translatable ramp assembly that includes a biasing member and a magnet coupled thereto, which is magnetically engaged with a guide post to provide a bias force at an interface of a lead screw and the ramp assembly. The bias force acts upon the interface by reducing a gap between outer threads of the lead screw and inner threads of a mating threaded interface structure of the ramp assembly that would otherwise cause lead screw hysteresis without the bias force.