Aromatic Hydrocarbon Grease Bearing for Hard Disk Reliability
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Solution Overview
Problem
Existing bearing devices for hard disks face issues with reading and writing errors due to foreign matter attachment, particularly oil droplets, caused by the outgassing of aliphatic hydrocarbon-based greases, which affect recording density and data transfer speeds.
Innovation Solution
A bearing device with a lubrication film using aromatic hydrocarbon-based grease, where the aromatic hydrocarbon content is 70 weight % or more, reducing the likelihood of oil droplet formation and attachment to the magnetic disk, thereby minimizing reading and writing errors. Additionally, using alkylnaphthalene as the base oil and lithium soap or lithium complex soap as the thickener enhances thermal resistance and oxidation stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aliphatic hydrocarbon-based grease is used to ensure durability, then the bearing device achieves high durability, but the grease generates outgas that condenses on the magnetic disk as oil droplets causing reading and writing errors
Solution Approach 1:
The patent changes the chemical composition parameter of the base oil from aliphatic hydrocarbon to aromatic hydrocarbon (specifically alkyl naphthalene). This parameter change fundamentally alters the outgas properties, preventing condensation on the magnetic disk while maintaining the lubrication function and durability of the bearing device.
2Manufacturing precision
If the floating quantity of the magnetic head is reduced to improve recording density, then the recording density improves, but foreign matter attachment to the magnetic head causes reading and writing errors
Solution Approach 1:
The patent converts the potential harm of grease outgas into a beneficial outcome by selecting aromatic hydrocarbon as the base oil. Instead of generating condensable outgas that forms harmful oil droplets, the aromatic hydrocarbon produces non-condensable outgas, thereby eliminating foreign matter attachment while allowing the use of reduced floating quantity for higher recording density.
3Ease of operation
If mineral oil mixed with poly-α-olefin is used as base oil, then the grease provides adequate lubrication, but the base oil and outgas scatter as oil droplets and attach to the magnetic disk
Solution Approach 1:
The patent changes the base oil parameter from mineral oil mixed with poly-α-olefin to pure aromatic hydrocarbon (alkyl naphthalene). This parameter change eliminates the oil droplet scattering phenomenon while maintaining adequate lubrication, as the aromatic hydrocarbon provides necessary lubrication without forming scatterable droplets.
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 aromatic hydrocarbon-based grease significantly reduces the occurrence of reading and writing errors by minimizing oil droplet formation and attachment, while alkylnaphthalene reduces evaporation, and lithium soap improves thermal resistance, leading to a more reliable and long-lasting bearing device.
Implementation Method 1
The outgas of aliphatic hydrocarbon has a problem in that the outgas is condensed on the magnetic disk of the hard disk, is attached as oil droplets
Implementation Method 2
alkylnaphthalene reduces evaporation
Implementation Method 3
lithium soap or lithium complex soap as the thickener enhances thermal resistance and oxidation stability
Data Source
AI summary
A bearing device has two or more bearings each having an inner ring and an outer ring disposed on the same axis. A ring-shaped holder is disposed between the inner ring and the outer ring and has circumferentially spaced-apart rolling element pockets with a concave grease pocket between each two adjacent rolling element pockets. Rolling elements are disposed in a rollable manner in respective ones of the rolling element pockets and a grease is stored in the grease pockets, the grease serving as a lubricant of the rolling element. The grease consists of at least a base oil comprised of aromatic carbon and a thickener, the content of the aromatic hydrocarbon being 70 weight % or more of the grease.