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Showing papers on "Fluid bearing published in 2002"


Journal ArticleDOI
TL;DR: In this paper, a load capacity test was conducted to determine how radial clearance variations affect the load capacity coefficient of foil air bearing and the results indicated that radial clearance has a direct impact on the performance of the bearing.
Abstract: Load capacity tests were conducted to determine how radial clearance variations affect the load capacity coefficient of foil air bearings. Two Generation III foil air bearings with the same design but possessing different initial radial clearances were tested at room temperature against an as-ground PS304 coated journal operating at 30,000 rpm. Increases in radial clearance were accomplished by reducing the journal's outside diameter via an in-place grinding system. From each load capacity test the bearing load capacity coefficient was calculated from the rule-of-thumb (ROT) model developed for foil air bearings. The test results indicate that, in terms of the load capacity coefficient, radial clearance has a direct impact on the performance of the foil air bearing. Each test bearing exhibited an optimum radial clearance that resulted in a maximum load capacity coefficient. Relative to this optimum value are two separate operating regimes that are governed by different modes of failure. Bearings operating with radial clearances less than the optimum exhibit load capacity coefficients that are a strong function of radial clearance and are prone to a thermal runaway failure mechanism and bearing seizure. Conversely, a bearing operating with a radial clearance twice the optimum suffered only a 20 percent decline in its maximum load capacity coefficient and did not experience any thermal management problems. However, it is unknown to what degree these changes in radial clearance had on other performance parameters, such as the stiffness and damping properties of the bearings.

134 citations


Book
25 Sep 2002
TL;DR: In this paper, a case study of composite bearing-Rolling element and fluid film in series non-Newtonian Viscoelastic Effects Orthopedic Joint Implants is presented.
Abstract: Classification and Selection of Bearings Lubricant Viscosity Fundamental Properties of Lubricants Principles of Hydrodynamic Lubrication Basic Hydrodynamic Equations Long Hydrodynamic Journal Bearing Short Journal Bearings Design Charts for Finite-Length Journal Bearings Practical Applications of Journal Bearings Hydrostatic Bearings Bearing Materials Rolling Element Bearings Selection and Design of Rolling Bearings Testing of Friction and Wear Hydrodynamic Bearings Under Dynamic Conditions Friction Characteristics Modeling Dynamic Friction Case Study: Composite Bearing-Rolling Element and Fluid Film in Series Non-Newtonian Viscoelastic Effects Orthopedic Joint Implants Appendix A: Units and Definitions of Material Properties Appendix B: Numerical Integration Bibliography Index

133 citations


Journal ArticleDOI
Luc Houpert1
TL;DR: In this paper, the miscellaneous components of bearing torque are described analytically, and the final tapered roller hearing torque is compared to hall hearing torque under various operating conditions.
Abstract: The miscellaneous components of bearing torque are described analytically. When the rolling element - race contact lengths are similar, the hydrodynamic ball bearing torque component can be similar to the tapered roller bearing one. In ball bearings, the sliding speed distribution encountered at the ball/race contact is the result of two torque contributions: curvature in space of the contact ellipse and spinning effects. These two torque contributions don't exist in tapered roller bearings. However, tapered roller bearings are subjected to a roller/rib torque which is compared analytically to the two previous hall hearing torque components. The final tapered roller hearing torque is compared to hall hearing torque under various operating conditions. It is shown that there are conditions for which the tapered roller hearing torque can he smaller than the hall hearing one; the latter point is demonstrated numerically and experimentally in reported literature. Presented at the 57th Annual Meeting Houston, T...

86 citations


Patent
18 Feb 2002
TL;DR: In this paper, a magnetic bearing is combined with a hydrodynamic bearing for axially conveying fluids, where the conveyor part is entirely magnetically borne and the radial bearing is provided with sufficient rigidity and efficiently dampened, whereby problems encountered when passing through critical speeds and the disadvantageous effects of hydrodynamics and mechanical imbalance of the rotor are avoided.
Abstract: A device for axially conveying fluids, wherein the conveyor part thereof is entirely magnetically borne and the radial bearing thereof is provided with sufficient rigidity and efficiently dampened, whereby problems encountered when passing through critical speeds and the disadvantageous effects of hydrodynamic and mechanical imbalance of the rotor are avoided. The magnetic bearing is combined with a hydrodynamic bearing.

81 citations


Journal ArticleDOI
TL;DR: In this article, the steady-state film pressures of hydrodynamic journal bearings were obtained by solving modified Reynolds equation based on the micropolar lubrication theory, with the help of the steady state film pressures, the steadystate performance characteristics in terms of load-carrying capacity, misalignment moment and friction parameter of a journal bearing were obtained at various values of eccentricity ratio.

74 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the dynamic characteristics of a herringbone grooved journal bearing with plain sleeve (GJPS) under static and dynamic load, and the results showed that a GJPS produces less friction torque than a PJGS.
Abstract: This research investigates the dynamic characteristics of a herringbone grooved journal bearing with plain sleeve (GJPS) and a plain journal bearing with herringbone grooved sleeve (PJGS) under static and dynamic load. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a journal, such as orbit or rotational speed, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. Numerical results are validated by the experimental results of prior researchers. A GJPS produces less friction torque than a PJGS so that the GJPS consumes less input power than the PJGS. Under static load, the PJGS converges to the fixed equilibrium position, but the GJPS has a whirling motion due to the rotating groove even at the steady state, which produces the excitation frequencies corresponding to the integer multiple of the rotor speed multiplied by the number of grooves. The variation of rotational speed of a GJPS is always less than that of a PJGS due to less friction torque. Under the effect of mass unbalance, the excitation frequencies of the reaction force in a GJPS and a PJGS are the rotational frequency due to mass unbalance and its harmonics due to the nonlinear effect of fluid film. However, the GJPS has relatively big amplitude corresponding to the multiples of the number of grooves, in comparison with the amplitudes at the adjacent harmonics.

65 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical study of the effect of surface roughness in hydrodynamic lubrication of a porous journal bearing with couplestress fluid as lubricant is made.

63 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigate if a solid lubricant coating applied to the surface of the bearing's top foil can function as a break-in coating and show that the presence of a top foil solid lubricants is effective at increasing the load capacity performance of the foil bearing.
Abstract: Foil air bearing load capacity tests were conducted to investigate if a solid lubricant coating applied to the surface of the bearing's top foil can function as a break-in coating. Two foil coating materials, a conventional soft polymer film (polyimide) and a hard ceramic (alumina), were independently evaluated against as-ground and worn (run-in) journals coated with NASA PS304, a high-temperature solid lubricant composite coating. The foil coatings were evaluated at journal rotational speeds of 30,000 rpm and at 25 C. Tests were also performed on a foil bearing with a bare (uncoated) nickel-based superalloy top foil to establish a baseline for comparison. The test results indicate that the presence of a top foil solid lubricant coating is effective at increasing the load capacity performance of the foil bearing. Compared to the uncoated baseline, the addition of the soft polymer coating on the top foil increased the bearing load coefficient by 120% when operating against an as-ground journal surface and 85 percent against a run-in journal surface. The alumina coating increased the load coefficient by 40% against the as-ground journal but did not have any affect when the bearing was operated with the run-in journal. The results suggest that the addition of solid lubricant films provide added lubrication when the air film is marginal indicating that as the load capacity is approached foil air bearings transition from hydrodynamic to mixed and boundary lubrication.

51 citations


Journal ArticleDOI
TL;DR: In this article, a new modified Reynolds equation is derived with a modified version of the hydrodynamic oil film being considered, together with a cavitation model, to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds.
Abstract: A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

44 citations


Journal ArticleDOI
TL;DR: In this paper, a review of compliant surface bearings in serving the needs of modern turbomachinery is made, which extends over a wide spectrum of severe operational and environmental conditions such as extreme low and high temperatures, speeds over 100,000 rpm and the use of cryogenics as lubricants.
Abstract: A review is made of the function of compliant surface bearings in serving the needs of modern turbomachinery. This service extends over a wide spectrum of severe operational and environmental conditions such as extreme low and high temperatures, speeds over 100,000 rpm, and the use of cryogenics as lubricants. The importance of using appropriate simulators that duplicate the actual equipment in evaluating the application of compliant bearings is demonstrated via two specific examples; one, a simulator to evaluate bearings for an air cycle machine and another for an advanced cryogenic device. In view of the known difficulties in using hydrodynamic bearings in vertical machines a new preloaded compliant journal bearing design is offered which performs as well with a vertically mounted shaft as it does in horizontal operation. In terms of the location of the first two rigid-body criticals, the test data show the compliant bearing's vertical operation to be at most 15 percent lower than for the horizontal case, whereas the maximum vibrational amplitude stayed the same for both modes of operation. This new class of hydrodynamic compliant surface journal bearings now makes possible development of oil-free machines capable of all attitude operation, such as aircraft gas turbine engines undergoing severe pitch maneuvers or machines that must be operated vertically due to space constraints.

43 citations


Patent
23 Sep 2002
TL;DR: In this article, a chemical mechanical belt polisher includes a hydrostatic fluid bearing that supports polishing pads and incorporates one or more of the following novel aspects: compliant surfaces surrounding fluid inlets in an array of inlets to extend areas of elevated support pressure around the inlets.
Abstract: A polishing system such as a chemical mechanical belt polisher includes a hydrostatic fluid bearing that supports polishing pads and incorporates one or more of the following novel aspects. One aspect uses compliant surfaces surrounding fluid inlets in an array of inlets to extend areas of elevated support pressure around the inlets. Another aspect modulates or reverses fluid flow in the bearing to reduce deviations in the time averaged support pressure and to induce vibrations in the polishing pads to improve polishing performance. Another aspect provides a hydrostatic bearing with a cavity having a lateral extent greater than that of an object being polished. The depth and bottom contour of cavity can be adjusted to provide nearly uniform support pressure across an area that is surrounded by a retaining ring support. Changing fluid pressure to the retaining ring support adjusts the fluid film thickness of the bearing. Yet another aspect of the invention provides a hydrostatic bearing with spiral or partial cardiod drain grooves. This bearing has a non-uniform support pressure profile but provides a uniform average pressure to a wafer that is rotated relative to the center of the bearing. Another aspect of the invention provides a hydrostatic bearing with constant fluid pressure at inlets but a support pressure profile that is adjustable by changing the relative heights of fluid inlets to alter local fluid film thicknesses in the hydrostatic bearing.

Journal ArticleDOI
TL;DR: In this article, the technical issues of hydrodynamic bearings (HDB) for hard disk drives (HDD) are discussed and results of numerical analysis and experiments aimed at solving the characteristic problems of high-speed HDDs.
Abstract: In this paper we discuss the technical issues of hydrodynamic bearings (HDB) for hard disk drives (HDD). We also report results of numerical analysis and of experiments aimed at solving the characteristic problems of high-speed HDDs.

Journal ArticleDOI
TL;DR: In this article, the principles of a continuously adjustable hydrodynamic bearing are described together with a comprehensive analysis model for studying its theoretical performance, including an expanded form of the governing Reynolds equation which took account of non-uniform variations in the fluid film thickness.
Abstract: Principles of a continuously adjustable hydrodynamic bearing are described together with a comprehensive analysis model for studying its theoretical performance. The model included an expanded form of the governing Reynolds equation which took account of non-uniform variations in the fluid film thickness. A solution procedure was devised whereby for a given set of adjustment conditions full simultaneously converged fields of fluid film thickness, temperature, viscosity and pressure would result, together with oil film forces. A wide range of operating characteristics were studied with results predicting advantages and benefits over conventional hydrodynamic bearings.

Journal ArticleDOI
TL;DR: In this paper, the tracking ability, the dynamic contact and friction forces of a tripad slider over a random wavy disk surface with 1 nm rms value in the near-contact regime were numerically investigated.
Abstract: We numerically investigated the tracking ability, the dynamic contact and friction forces of a 2-DOF model of a tripad slider over a random wavy disk surface with 1 nm rms value in the near-contact regime. The air bearing was modeled as a lumped spring and dashpot in order to consider a general design methodology of the flying slider in the near-contact regime. The nominal flying height was changed from the contact regime to the near-contact regime. We studied the effects of the front and rear air bearing stiffnesses, the nominal flying height and the friction coefficient on the tracking ability and contact force. As a result, we found that the spacing variation is caused not only by the slider dynamics but also by the micro-waviness of the disk surface and the distance of the contact pad (head-gap) position from the rear air bearing center We also derived the closed form frequency response functions of the spacing variation to the disk surface waviness. The approximation agreed with the numerical simulation. The effect of the friction coefficient on the tracking ability can be neglected when the flying height is more than 1 nm.

Patent
28 Jun 2002
TL;DR: In this article, a bearing system in which an axially stiff narrow gap fluid dynamic gas bearing is preloaded by an Axially less stiff larger gap fluid-dynamic bearing is described.
Abstract: A bearing system in which an axially stiff narrow gap fluid dynamic gas bearing is preloaded by an axially less stiff larger gap fluid dynamic bearing. As an example two fluid dynamic bearings are provided spaced apart along a shaft, one of the bearings comprising a fluid dynamic bearing, the other comprising an air bearing. The fluid dynamic bearing has a larger gap, while the air bearing has a relatively small gap. The overall working surface area of the air bearing may be twice as much or more than the working surface area of the fluid bearing.

Journal ArticleDOI
Byoung-Hoo Rho1, Kyung-Woong Kim1
TL;DR: In this article, synchronous control of bearing is employed through a control algorithm for an actively controlled hydrodynamic journal bearing in order to suppress whirl instability and to reduce the unbalance response of a rotor-bearing system.

Journal ArticleDOI
TL;DR: In this paper, the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications were tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally enlarged clearance to simulate a worn condition.
Abstract: Test results are presented for the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications. The bearing is tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally enlarged clearance to simulate a worn condition. Test data are presented at 24,600 rpm, with supply pressures of 4.0, 5.5, and 7.0 MPa, and eccentricity ratios from 0.1 to 0.5 in 0.1 increments. Overall, the results suggest that neither a single plugged orifice nor significant wear on the bearing land will disable a well-designed hybrid bearing. These results do not speak to multiple plugged orifices and are not an endorsement for operations without filters to prevent plugging orifices.

Journal ArticleDOI
TL;DR: In this article, the effects of micro-textures on air film dynamic characteristics of flying head slider bearings are modeled as deterministic rectangular models in the transverse and longitudinal directions, and the effect of transverse microtextures' spacing and depth on the air film dynamics are also numerically investigated.
Abstract: This paper describes the air film dynamics for micro-textured flying head slider bearings in magnetic hard disk drives and it discusses their ability to increase the air film damping. In order to study the effects of micro-textures on air film dynamic characteristics of flying head slider bearings, two-dimensional micro-textures are modeled as deterministic rectangular models in the transverse and longitudinal directions. Dynamic analysis of these micro-textured flying head slider bearings is carried out by computing the impulse responses of the sliders and applying the modal analysis method to obtain their modal frequencies, damping ratios, and mode shapes. It is found that micro-textures on air bearing surfaces in the transverse direction have very significant effects and increase the air film damping of the slider's three vibration modes but do not affect the air film stiffness. The same is not true for micro-texture in the longitudinal direction. The effects of transverse micro-textures' spacing and depth on the air film dynamics are also numerically investigated in detail. The optimum values for high air film damping ratios are obtained. It is found that transverse micro-textures having small spacing are not very effective, being equivalent to the surface roughness effect.

Journal ArticleDOI
TL;DR: In this article, the effects of surface roughness on a narrow porous journal bearing were studied using Christensen's stochastic theory, and an exact solution for the film pressure and pressure in the bearing material was given for arbitrary wall thickness.

Journal ArticleDOI
TL;DR: In this paper, the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location were numerically analyzed and the results showed that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.
Abstract: This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing (PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT), and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or axial displacement of a rotor, are determined by solving its nonlinear equations of motion with the Runge–Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

Journal ArticleDOI
TL;DR: In this paper, an extended computational bulk flow analysis for prediction of performance in angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings is presented, where the fluid motion within the thin film lands is governed by mass conservation and momentum transport equations.
Abstract: An extended computational bulk-flow analysis for prediction of performance in angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings is presented. The fluid motion within the thin film lands is governed by mass conservation and momentum transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. A perturbation analysis for small amplitude shaft axial motions and angulations leads to zeroth and first-order equations describing the equilibrium and perturbed fluid flows. The computational procedure predicts the bearing flow rate, thrust load and restoring moments, drag torque, and 27 force and moment coefficients. The effects of misalignment on the dynamic performance of a refrigerant fluid-hybrid thrust bearing are evaluated at an optimal operating condition. The axial force/displacement stiffness coefficient and the direct moment/angle stiffness coefficients show a maximum for a certain recess pressure ratio, while the damping coefficient steadily increases with the applied load. As the misalignment angle increases, both moment and force coefficients also increase. Most operating conditions show a whirl frequency ratio equal to 0.50. Thus, thrust hybrid bearings offer the same limited stability characteristics as hydrodynamic thrust bearings when undergoing self-excited shaft angular motions.

Journal ArticleDOI
TL;DR: In this paper, the combined influence of surface roughness and journal misalignment on the performance of an orifice compensated hole-entry hybrid journal bearing system is theoretically studied, and the results indicate that the effect of journal mis alignment is to lower the value of the minimum fluid-film thickness of the journal bearing, while the effect is to partially compensate this loss.
Abstract: The combined influence of surface roughness and journal misalignment on the performance of an orifice compensated hole-entry hybrid journal bearing system is theoretically studied. The analysis considers the average Reynolds equation for a rough surface for the solution of the lubricant flow field in the clearance space of a journal bearing system. The bearing performance characteristics are presented for the various representative values of surface roughness parameter (Λ) and surface pattern parameter (γ) for a concentric design pressure ratio β* = 0.5. Performance is also compared to capillary and constant flow valve compensated bearings. The computed results indicate that the effect of journal misalignment is to lower the value of the minimum fluid-film thickness of the journal bearing system while the effect of surface roughness is to partially compensate this loss. For the chosen values of journal misalignment parameters (ϕ, δ), the constant flow valve compensated symmetric journal bearing configurat...

Patent
23 Dec 2002
TL;DR: In this article, a low-torque lubricating oil for bearings and fluid dynamic bearing, porous oil-impregnated bearings and hydrodynamic type porous oil impregnated bearing is presented.
Abstract: There is provided a durable low-torque lubricating oil for bearings and fluid dynamic bearings, porous oil-impregnated bearings and hydrodynamic type porous oil-impregnated bearings suitable for use as bearings in small-sized spindle motors for information equipment. The lubricating oil composition comprising (A) a diester of a monovalent aliphatic alcohol containing 6-10 carbon atoms and a saturated aliphatic dicarboxylic acid containing 10 carbon atoms as base oil and (B) 3-20% by weight of a low-viscosity lubricating oil with a kinematic viscosity of less than 11 mm 2 /s at 40 ° C., a fluid dynamic pressure bearing unit or a porous oil-impregnated bearing unit containing said lubricating oil composition or a spindle motor provided with said bearing unit.

Journal ArticleDOI
TL;DR: In this paper, the effect of surface roughness on the performance of a capillary compensated hole-entry hybrid journal bearing system has been theoretically studied, and the impact of surface irregularity on the bearing performance has been analyzed for transverse, isotropic and longitudinal surface patterns.

Journal ArticleDOI
TL;DR: A numerical scheme that has been successfully used to solve a wide variety of compressible flow problems is extended to predict the effects of gaseous cavitation in moderate to heavily loaded bearings to demonstrate the superior ability of the method to solve such problems.
Abstract: A numerical scheme that has been successfully used to solve a wide variety of compressible flow problems, titled the space-time conservation element and solution element method, is extended to predict the effects of gaseous cavitation in moderate to heavily loaded bearings. The formulation of the one-dimensional problem is presented. The numerical results obtained for different types of bearings are compared with other numerical solutions to demonstrate the superior ability of the method to solve such problems. Presented at the 56th Annual Meeting in Orlando, Florida May 20–24, 2001

Journal Article
TL;DR: In this article, an analytical solution for a hydrostatic porous journal bearing was developed for low eccentricity, low permeability and low bearing length-to-diameter ratio as compared with the numerical solution of the Reynolds equation.
Abstract: An approximate solution for a hydrostatic porous journal bearing is developed. The analytical approximation is valid for low eccentricity, low permeability and low bearing length-to-diameter ratio as compared with the numerical solution of the Reynolds equation. The maximum deviation between the approximate solution and numerical solution is within 10% for an eccentricity ratio a less than 0.5, a porous feeding parameter A less than 1.0 and a length-to-diameter ratio (LID) less than 0.5. The approximate solution provides an easy and convenient method to estimate the performance of hydrostatic porous journal bearings.

Journal ArticleDOI
TL;DR: In this study, the hybrid search algorithm for a multi-variable design exhibits better efficiency compared with the search efficiency by using the SM, and eliminates the need of several trials with random initial guesses to ensure high probability of global optimization.
Abstract: The study deals with the development of a hybrid search algorithm for efficient optimization of porous air bearings. Both the compressible Reynolds equation and Darcy's law are linearized and solved iteratively by a successive-over-relaxation method for modeling parallel-surface porous bearings. Three factors affecting the computational efficiency of the numerical model are highlighted and discussed. The hybrid optimization is performed by adopting genetic algorithm (GA) for initial search and accelerated by simplex method (SM) for refined solution. A simple and useful variable transformation is presented and used to convert the unconstrained SM to a constrained method. In this study, the hybrid search algorithm for a multi-variable design exhibits better efficiency compared with the search efficiency by using the SM. The proposed hybrid method also eliminates the need of several trials with random initial guesses to ensure high probability of global optimization. This study presents a new approach for op...

Journal ArticleDOI
J. K. Martin1
01 Jan 2002
TL;DR: In this paper, the principles of a continuously adjustable hydrodynamic bearing concept are outlined and the governing Reynolds equation is given, taking into account non-uniform variations in the fluid film thickness.
Abstract: Principles of a continuously adjustable hydrodynamic bearing concept are outlined and the governing Reynolds equation is given. The equation is non-dimensionalised and expanded taking into account non-uniform variations in the fluid film thickness. Also given are observations of predicted operating characteristics of one form of the bearing.

Patent
08 Oct 2002
TL;DR: In this paper, a fluid dynamic bearing on a thrust plate of a hub/shaft/thrust plate assembly suitable for use in ultra small form factors having limited axial space is presented.
Abstract: The present invention provides a fluid dynamic bearing on a thrust plate of a hub/shaft/thrust plate assembly suitable for use in ultra small form factors having limited axial space.

Patent
13 Jun 2002
TL;DR: In this article, a hydrodynamic bearing according to the present invention has different diameter sizes by positions so that overflow or splashing of lubricant out of the apparatus is prevented due to a centrifugal force during high-speed rotation.
Abstract: In a hydrodynamic bearing according to the present invention a fixed shaft has different diameter sizes by positions so that overflow or splashing of lubricant out of the apparatus is prevented due to a centrifugal force during high-speed rotation, and lubricant reservoirs are provided in narrower clearances and in wider clearances so that the lubricant is induced to move toward lubricant reservoirs in narrower clearances due to surface tension while the hydrodynamic bearing is in stop, therefore overflow of the lubricant is prevented at the time of starting up.