Disk Drive Pivot Bearing Radial Stiffness via Rolling Contact

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Solution Overview

Problem

Conventional pivot bearings in disk drives face a conflict between achieving high radial stiffness for improved dynamic performance and maintaining low rotational resistance, leading to contamination issues and difficulty in rework, while also requiring minimal torque for rotation.

Innovation Solution

A pivot bearing design featuring two connected shafts with a preloaded connection band, where the rotatable shaft rolls against the fixed shaft, maintaining constant relative distance and curvature to ensure consistent rotational resistance, and a band with prestressed legs for enhanced stiffness without increased torque requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional ball bearings are tightly jammed against race surfaces to increase radial stiffness, then radial stiffness is improved, but rotational resistance increases and friction is generated

Engineering Contradiction:

Improveradial stiffnessVSAvoidrotational resistance

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent replaces the conventional ball bearing mechanical system with a magnetic field-based system. Magnets embedded in the inner race interact with ferromagnetic material on the outer race, creating magnetic attraction forces that provide radial stiffness without physical contact. This eliminates friction and rotational resistance while maintaining the required stiffness, directly resolving the contradiction between radial stiffness and rotational resistance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If conventional bearings are press-fitted to increase stiffness, then radial stiffness is improved, but particulate contamination is generated

Engineering Contradiction:

Improveradial stiffnessVSAvoidparticulate contamination

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The magnetic bearing system eliminates the need for press-fitting and mechanical interference fits. The magnets are embedded in the inner race and create magnetic fields that hold the outer race in position, providing stiffness without mechanical contact that would generate particulate contamination. This non-contact magnetic coupling prevents the scoring and scraping that occurs in conventional press-fit bearings.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If ball bearings are positioned with gaps to reduce friction, then rotational resistance is reduced, but radial stiffness decreases and play is introduced

Engineering Contradiction:

Improverotational resistanceVSAvoidradial stiffness

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The magnetic bearing system uses magnetic attraction forces to provide radial stiffness without requiring physical contact or eliminating gaps. The magnets in the inner race create a magnetic field that attracts the ferromagnetic outer race, maintaining stiffness while allowing the bearing elements to remain separated, thus avoiding friction and rotational resistance associated with tight mechanical fits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The design achieves increased radial stiffness while maintaining low rotational torque and minimizing contamination, allowing for precise actuator control and easy rework without sacrificing frictionless operation.

Implementation Method 1

a preloaded connection band, where the rotatable shaft rolls against the fixed shaft, maintaining constant relative distance

Methodology Applied

Scientific EffectPrestress: Tension

Implementation Method 2

said second member being pivotable about said first stationary member by rolling contact of a bearing surface of said first member against a corresponding bearing surface of said second member

Methodology Applied

Scientific EffectRolling contact: Roller

Data Source

PatentUS7515385B1Band pivot bearing

Publication Date: 2009.04.07 SEAGATE TECHNOLOGY HDD HOLDINGS

AI summary

A pivot bearing for an actuator assembly of a disk drive includes a first stationary member, a second pivoting member, and a third flexible member interconnecting the first and second members. The first stationary member is secured preferably between the base and top cover of the drive, while the second pivotal member is secured to the actuator. The second pivoting member rotates about the stationary member, and the third flexible member bends in response to the pivoting action of the second member. Rolling contact occurs between bearing surfaces of the first and second members. Overall bearing stiffness is increased with use of the bearing, and particularly radial stiffness. Increased bearing stiffness enhances system mode frequency and thereby improves bandwidth capability for a disk drive.