R. Kaneko

A Database for Interpolation of Poiseuille Flow Rates for High Knudsen Number Lubrication Problems

We propose the use of a Poiseuille flow rate database for rapid calculation of a generalized lubrication equation for high Knudsen number gas films. The database is created by numerical calculations based on the linearized Boltzmann equation. The proposed interpolation method is verified to reduce calculation time to several tenths of that required to perform rigorous calculations with the same accuracy

Dynamic Characteristics of Gas-Lubricated Slider Bearings Under High Knudsen Number Conditions

This paper presents numerical analyses of the dynamic characteristics of gas-lubricated slider bearings under high Knudsen number conditions using a generalized lubrication equation based on the Boltzmann equation. The present analysis is applied to the dynamic response of flying head sliders for magnetic disk storage devices. For a small slider with ultra-thin spacing, the deviations of the slip flow approximation equations are remarkable in regard to steady flying characteristics, but insignificant in regard to dynamic characteristics

Design of negative pressure slider for magnetic recording disks

This paper reports on investigations of static and dynamic characteristics of a negative pressure slider for magnetic recording disks. The negative pressure slider is composed of two narrow pressure pads, as on a cylindrical slider, separated by a rather large reverse step region. Through a modified Reynolds equation, which considers slip flow effects, the static and dynamic pressure distributions are calculated by divergence formulation and a finite difference method. Using the calculated results, the optimum reverse step depth is clarified in terms of both dynamic characteristics and wear caused by starting and stopping in contact with the disk. With a 4.6 mm length, 3.2 mm total pad width and 4 μm reverse step depth, the negative pressure slider has six times the air film stiffness of a conventional light load slider. Experimental data concerning spacing versus reverse step depth and take-off characteristics for the negative pressure slider in submicron spacing region are in good agreement with the calculated results.

Analysis of flying characteristics of magnetic heads with ultra-thin spacings based on the Boltzmann equation

Numerical analyses of flying characteristics of magnetic heads for magnetic disk storage with ultrathin spacings are presented, applying the general lubrication equation based on the Boltzmann equation as an exact solution. The analyses are then compared with those using the slip flow approximation equations with accommodation coefficients of momentum. For conventional magnetic heads with nominal submicron spacings, differences between flying characteristics based on the generalized equation and the approximation equation are not necessarily significant (10% or less). This can explain why the experimental results agree well with numerical solutions based on a slip flow approximation. The differences for small heads with ultrathin spacings (less than 0.1 mu m) can be more than 20%, indicating that for such heads the generalized lubrication equation based on the Boltzmann equation should be used to predict the flying characteristics for slider designs. >

Estimation of gas film lubrication effects beneath sliding bushings of microrotors using a molecular gas film lubrication equation

Abstract Molecular gas film lubrication effects between rotor bushings and stators in micromotors with a spacing of less than 0.1 μm are numerically clarified using a molecular gas film lubrication equation based on the Boltzmann equation. In conventional bushings, positive pressures and negative pressures are generated nearly equally and the net sum, and hence the load-carrying capacity, is extremely small so it cannot support the rotor weight. A new bushing with a step produces a net pressure that results in a load-carrying capacity that exceeds the rotors weight. Gas film lubrication effects considering surface roughness are briefly discussed on the basis of the mixed lubrication model.