Showing papers on "Fluid bearing published in 2005"

Fluid dynamic bearing system

Abstract: The invention relates to a fluid dynamic bearing system that comprises at least one stationary part that has a shaft and two bearing plates disposed on the shaft at a mutual spacing, and at least one rotating part that is supported so as to rotate about a rotational axis with respect to the stationary part, and comprises a bearing bush and a sleeve enclosing the bearing bush. A bearing gap filled with bearing fluid is provided between the parts and at least one sealing gap for sealing the bearing gap that extends concentric to the rotational axis. The bearing comprises at least one fluid dynamic radial bearing and two fluid dynamic axial bearings and at least one recirculation channel that connects the two axial bearing regions to each other. According to the invention, the largest radial diameter of the recirculation channel is greater than or equal to the largest diameter of the sealing gap, and the smallest radial diameter of the recirculation channel is greater than or equal to the largest diameter of an adjacent bearing plate. Moreover, additional and effective deairing of the recirculation channel is effected by a venting device. To realize improved equilibrium of pressure in the bearing gap and improved retention of the bearing fluid, the sealing gaps can be inclined, at least in sections, at an angle α, β with respect to the rotational axis, wherein the angles may have different sizes.

Integral motor and air bearing cooling path

Abstract: A motor is provided including a housing having single and integral motor and bearing cooling inlets. The motor is arranged within the housing and includes a stator and a rotor assembly supported on air bearings. The cooling inlet is in fluid communication with the motor stator and with the air bearings. The motor cooling inlet provides and the bearing cooling inlet provides a uniform pressure on the rotor assembly. The uniform pressures exerted on the rotor assembly produce bearing loads that generally cancel one another. The source of the cooling flow is uncompressed air at low pressure. This may be achieved by providing a vent in the housing that is common to both the motor cooling inlet and the bearing cooling inlet. As a result, journal bearings and seals of substantially the same size may be used.

Demonstration of a turbojet engine using an air foil bearing

Abstract: A test of the target drone main propulsion turbojet engine was recently conducted that demonstrated successful operation of a turbojet engine with a compliant foil air bearing. For this effort, the hot section rolling element bearing and the entire existing lubrication system was replaced with a compliant foil air bearing. This technology demonstration test showed the ability of the foil bearing to operate in the extremely challenging environment behind the turbine. Detailed engine integration studies, bearing component rig testing and hot engine simulator tests were completed prior to the successful engine test. The rig and simulator tests verified high temperature capabilities of the bearing and its surface coating, the bearing journal design, bearing dynamic performance, and rotor-bearing system dynamic stability, prior to engine integration and test. Based on these preliminary efforts, the engine and bearing were assembled and tests were conducted that included over 70 start stop cycles (including hot restarts), seven simulated mission cycles and more than 14 hours of run time. The foil bearing and engine operated flawlessly throughout the test. Vibrations were very low and all temperatures and pressures were as expected. A posttest tear down and hardware inspection revealed that the bearing, journal and all components remained in perfect condition. These data will be used to further the application of foil bearings to numerous other gas turbine engines for both military and commercial systems.Copyright © 2005 by ASME

Development of high-speed micro-gas bearings for three-dimensional micro-turbo machines

Abstract: A micro-high-speed bearing test rig has been designed and fabricated to develop air bearings for a micro-machine gas turbine. The micro-machine gas turbine requires bearings of diameter 4 mm to operate stably at 870 000 rpm. Based on the preliminary analysis, it has been found that a large bearing gap and very high rotor balance are required to achieve low viscous loss at high speed and to prevent the rotor from hitting the bearing at critical speed. Therefore, a hydro-inertia gas bearing has been selected with half-split bearing sleeves. A hydro-inertia bearing is a type of static air bearing which has large bearing clearance to generate supersonic flow in the bearing gap. Currently, a rotor speed as high as 770 000 rpm has been achieved in the test.

On the Lift-off Speed in Journal Bearings

Abstract: The development and exploration of the Stribeck curve have a long history. It originated based on a series of experiments that were devoted to the characterization of the behavior of fluid-film bearings, which proved to be useful for defining the boundary, mixed and hydrodynamic lubrication regimes. In this paper, we present the results of a series of experiments with a journal bearing operating under different loads and oil inlet temperatures. Of interest in the present study is to explore the behavior of lift-off speed and the factors that affect it. An equation is proposed to predict the lift-off speed. Its results are compared with Vogelpohl’s equation.

Effects of lubricant additives on the performance of hydrodynamically lubricated journal bearings

Abstract: A non-Newtonian rheological model to investigate theoretically the effects of lubricant additives on the steady state performance of hydrodynamically lubricated finite journal bearings is introduced. In this model, the non-Newtonian behavior resulting from blending the lubricant with polymer additives is simulated by Stokes couple stress fluid model. The formed boundary layer at the bearing surface is described through the use of a hypothetical porous medium layer that adheres to the bearing surface. The Brinkman-extended Darcy equations are utilized to model the flow in the porous region. A stress jump boundary condition is applied at the porous media/fluid film interface. A modified form of the Reynolds equation is derived and solved numerically using a finite difference scheme. The effects of bearing geometry, and non-Newtonian behavior of the lubricant on the steady-state performance characteristics such as pressure distribution, load carrying capacity, side leakage flow, and coefficient of friction are presented and discussed. The results showed that lubricant additives significantly increase the load carrying capacity and reduce both the coefficient of friction and the side leakage as compared to the Newtonian lubricants.

Numerical and Experimental Investigations on Flexible Multi-bearing Rotor Dynamics

Abstract: An experimental test rig is built to verify the dynamics of a multi-bearing rotor It consists of two flexibly coupled shafts and is connected to a motor at one end via a flexible coupling. Each of the shafts is supported at the ends by two hydrodynamic bearings and is attached with two disks with equal and unequal masses, respectively. The mathematical model of the test rig is developed and is simulated numerically. The non-stationary dynamic responses of the system during speed-up with a constant angular acceleration are shown, respectively, by the non-stationary bifurcation diagrams, the selected time flows, and the spectrum cascades. Experiments are then carried out on the test rig. Generally, the numerical results are verified qualitatively by the experiments. Both results indicate that the non-synchronous whirls of the two shafts influence each other when flexibly coupled together. In particular, a new phenomenon is found for the four-bearing rotor system: the pre-existing non-synchronous whirl/whip resulted from the instability of one shaft can activate the onset of oil instability of another shaft. In the theoretical simulation, this phenomenon represents the rapid increase of the non-synchronous whirl orbit, whereas in the experiment, it represents the simultaneous existence of two whirl/ whip frequencies in the spectra.

Hydrodynamic performance of a thrust bearing with micropatterned pads

Abstract: The primary objective of this study was to investigate the influence of surface texturing on hydrodynamic lubrication of tilting-pad thrust bearings in terms of bearing power loss, operating temperature, and oil-film thickness. For this purpose, the working faces of six thrust pads from a 228.6-mm-outer-diameter bearing were textured. The textured surface consisted of a system of crossing channels of less than 10 μm in depth. Tests were conducted with a VG68 mineral turbine oil supplied to the bearings at a constant temperature of 50°C and flow rate of 15 L/min. The following parameters were measured: frictional torque, pad and collar temperatures, oil-film thickness, and pressure profiles along two circumferential lines. No significant change in collar and pad temperature could be observed when the patterned bearing was used. However, the textured bearing showed a tendency to exhibit lower power loss especially when an optimum oil flow supply rate was used. At the same time, inlet and outlet film thickne...

Design of Hydrodynamic Bearing for Miniature Hard Disk Drives

Abstract: This paper has two specific goals to achieve. The first goal is to address major challenges encountered in design and development of miniature hydrodynamic bearings for small form factor hard disk drive spindle motors. These challenges include extremely small thickness of the spindle motors, mass productivity of tiny bearing parts, and bearing reliability and performance in relation to changes in atmospheric pressure. To overcome these challenges, we have developed a prototype hydrodynamic bearing that is resistant to environmental changes, free from oil film disruption, and tolerant of variations in processing precision. The prototype hydrodynamic bearing has two special features: an oil circulation function and a gas/liquid separation function. The oil circulation function is achieved by using asymmetric hydrodynamic grooves together with circulation passages. The gas/liquid separation function is achieved by using tapered capillary seals in the circulation passages. As a result of these two special features, the prototype hydrodynamic bearing can successfully expel air bubbles out of the bearing, thus enhancing the performance and reliability of the hydrodynamic bearing. The second goal is to evaluate the prototype hydrodynamic bearing in a miniature spindle motor for small form factor hard disk drives. Two specific bearing designs are evaluated. The first bearing design is a pushing type that generates no low-pressure area. However, the flow rate increases at high temperature. The second design is just the opposite. It is a pulling type design that generates a low-pressure area. But the flow rate is constant and is independent of temperature changes. To accommodate manufacturing tolerances, a parametric study is conducted to identify the effects of manufacturing tolerance on bearing performance.

Experimental Characterization of the Influence of Coating Materials on the Hydrodynamic Behavior of Thrust Bearings: A Comparison of Babbitt, PTFE, and PFA

Abstract: The present paper is the first of a series dealing with the experimental characterization of the coating materials' influence on the hydrodynamic behavior of thrust bearings. This paper presents a unique set of experimental data characterizing the influence of material coating on hydrodynamic oil films. The data are presented for extensive experimental conditions in which the load, the rotation speed, and the temperature were systematically varied. Seven main parameters characterizing the oil film were recorded. One metallic coating (Babbitt) and two Teflon-based coatings (polytetrafluoroethylene and polyperfluoroalkoxyethylene) were tested. It was clearly evidenced that the nature of the material strongly influences the hydrodynamic behavior. As expected in the hydroelastic regime, coatings with different properties (i.e., metals versus polymers) exhibit strong differences in their hydrodynamic behavior The originality of the paper lies, however, in that the two polymers showed very different behavior.

Spindle motor having a hydrodynamic bearing system

Abstract: The invention relates to a spindle motor having a hydrodynamic bearing system, particularly to drive platters in a hard disk drive, the platters being disposed on a rotor, and the bearing system being formed by a bearing sleeve arranged on a baseplate and a shaft rotatably supported in an opening in the bearing sleeve and at least one thrust plate connected to the shaft. A liquid lubricant is filled into a bearing gap formed between the shaft, the thrust plate and the bearing sleeve. The invention is characterized in that the thrust plate rests directly against the rotor and is accommodated in an annular recess in the bearing sleeve facing the rotor.

A design model for circular porous air bearings using the 1D generalized flow method

Abstract: Although the working principles of porous air bearings have been known for many years, most calculation procedures still involve specialized 3D CFD techniques which are not very useful to design engineers who initially require first-order engineering models for feasibility studies. This paper presents a simple design model for a circular porous air bearing based on well-established 1D generalized flow theory. Understanding porous air bearing mechanics is relatively easy with the proposed design model because it captures the essential physical phenomena governing the airflow. Moreover, the 1D model has a very simple architecture that allows easy design synthesis and requires minimal computational requirements. Comparison with experimental data shows accuracy comparable to specialized 3D techniques.

Numerical simulation of slider air bearings based on a mesh-free method for HDD applications

Abstract: This paper focuses on the development of a computational method to be used as a tool for air bearing simulation and design in modern hard disk drive. A data density of 100 Gb/in.2 has already been achieved in today’s production. The hard disk drive industry’s next goal is to increase the data density to 1 Tb/in.2 . New features in air bearing designs include shaped rails, multiple etching depths and negative pressure pockets. Thus, mesh generation is a difficult task in the air bearing simulation. This, in turn, demands the development of an accurate and easy-to-use computational method to solve Reynolds equations based on various flow models. Least square finite difference scheme, one of mesh-less methods, is presented to solve the slider air bearing problems of hard disk drives. For each specified attitude, the air bearing pressure is obtained by solving the Reynolds equation using the mesh-free method. The discretized nonlinear systems of equations are solved by successive over-relaxation (SOR) implementation, and the results of the numerical solutions are compared with other numerical and experimental data.

Current Status of Hybrid Bearing Damage Detection

Abstract: Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high pressure oxidizer turbopump, on the space shuttle main engine, led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si3N4 balls. The aerospace industry is currently studying the use of hybrid bearings and naturally the failure modes of these bearings become an issue in light of the limited data available. In today s turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Since the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure. The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris, in oil, using a commercial particle counter.

Fixed shaft type fluid dynamic bearing motor

Abstract: A fixed shaft type fluid dynamic bearing motor having two interfaces of a lubricating fluid, in which a channel leading from near the top end of the inner periphery of a rotating sleeve to near the periphery of the bottom of the sleeve is formed in the sleeve. The lubricating fluid near the top end of the inner periphery of the sleeve is thrown out into the channel by centrifugal force, and further conveyed to near the periphery of the bottom of the sleeve by centrifugal force and/or by slanted channel in circumferential direction. A dynamic-pressure generating groove for pumping the lubricating fluid toward the top end of the sleeve is formed between the fixed shaft and the sleeve. The dynamic-pressure generating groove and the centrifugal force cause the circulation of the lubricating fluid, thereby sealing the lubricating fluid. For bearing configuration, a cone bearing or a cylindrical bearing can be used to achieve a low profile. The axial space smaller than that of tapered seals can be utilized to achieve a low-profile recording disk drive.

Oil-film thickness and temperature measurements in PTFE and babbitt faced tilting-pad thrust bearings

Abstract: The influence of pad facing material on hydrodynamic lubrication in tilting-pad thrust bearings is investigated in terms of pad and oil-film temperatures and thicknesses. Two tilting-pad thrust bearings are examined: one with babbitt pad facing, the other with a layer of PTFE-based composite material. Frictional torque, pad, collar, and oil-film temperatures and thicknesses are all monitored by means of a comprehensive array of sensors mounted in the bearing and shaft.A considerably smaller range of temperature is seen in the steel backing immediately below the surface material for the PTFE faced pads. Oil-film temperatures measured at the mid-point on the pad trailing edge show no significant difference between the two bearings. Oil-film thicknesses in the two bearings are seen to differ. At the leading edge, oil-film thickness is thinner for the PTFE pad than for babbitt. However, at the trailing edge the PTFE pad has the thicker film.

Design and development of orifice-type aerostatic thrust bearing

Abstract: Air bearings are extensively used in pre- cision machines and equipment in recent years. Unlike conventional bearings, there is no physical contact between the sliding surfaces. The moving surface can glide smoothly on the other surface, minimising the control effort to achieve high accuracy and precision. Analytical study was carried out avoiding complexi- ties in the formulation. The governing parameters were kept at a minimum. This helped in easy under- standing of the dynamics and performance behavior of the air bearings. A simple design methodology was also developed to assist in the design or the selection process of the bearing. Finally, a three-dimensional (3D) model was built for Computational Fluid Dy- namics (CFD) analysis to verify the theoretical result. A test set-up was designed to measure and study the static and dynamic performance of different kind of air bearings for future air bearing development. More- over, the experimental data were also taken and com- pared with the analytical results.

Dynamic-pressure fluid bearing device, motor, recording disk drive device, and assembling tool

Abstract: PROBLEM TO BE SOLVED: To prevent a leakage of a lubricating agent filled in a bearing part and air bubbles intruding inside the bearing part even when an open end of the bearing part is blocked by a finger upon assembling a dynamic-pressure fluid bearing device. SOLUTION: The dynamic-pressure fluid bearing device 4 is equipped with a shaft 41, a second thrust flange 41c, a sleeve 42, a radial bearing part 71, and a thrust bearing part 73. The second thrust flange 41c is fixed near one end of the shaft 41. A third cylindrical projection 42e projecting in the axial direction more than the second thrust flange 41c is provided on one end side of the sleeve 42 fixedly or by integral processing. A cutout part 50 communicating with a radial direction inside space and a radial direction outside space partitioned by the third cylindrical projection 42e is provided to the third cylindrical projection 42e. COPYRIGHT: (C)2007,JPO&INPIT

Hydroinertia gas bearings for micro spinners

Abstract: Externally pressurized gas bearings with large bearing clearance are successfully used in ultra-high-speed micro spinners. For example, a micro spinner 4 mm in diameter is stably operated at more than 20 krps and its whirl ratio exceeds 20. In such bearings, the inertia effect of the gas flow in bearing clearance becomes predominant and its Mach number exceeds 1. As a result, gas pressure in the bearing clearance becomes negative. These bearings are called hydroinertia gas bearings, in contrast to the conventional hydrostatic gas bearings. Static characteristics of hydroinertia gas bearings are analyzed by considering the viscous effect of gas as wall friction, and the optimum design of hydroinertia gas bearings is shown. Experimental results on micro spinners and trial design of hydroinertia gas bearings for micro gas turbines are also discussed.

Pressure Measurements for Translating Hydrostatic Thrust Bearings

Abstract: The objective of this study is to take insitu measurement of the pressure profile that exists between a sliding thrust bearing and a stationary thrust surface. Using a two-dimensional model of the bearing and the classical one-dimensional Reynolds equation, the experimental results are explained and the minimum fluid film thickness and the tilt angle of the bearing are numerically determined. In this work, it is shown that the bearings tilt into the leading edge of the bearing and that the minimum fluid-film thickness at the leading edge of the bearing is on the order of the surface roughness. This work provides fundamental insight into the problem of metal-to-metal contact for thrust bearings.

Hydrodynamic Characteristics of ER Journal Bearings with External Electric Field Imposed on the Contractive Part

Abstract: The hydrodynamic characteristics of journal bearings with electrorheological (ER) fluid lubrication are studied in this article. The external applied electric field is partially imposed on the contractive part (arcwise) of the journal bearings. The bearing has a finite length and operates under incompressible laminar flow with steady conditions. The full three-dimensional Navier-Stokes (N-S) equations are solved numerically. The modified Bingham plastic model is used to describe the behavior of the ER fluid. In this study, the cavitation effects are also considered using viscosity modeling. The effects of electric field and eccentricity on the performance of journal bearings are investigated comprehensively.

Fluid Dynamic Pressure Bearing, Spindle Motor and Storage Disk Drive Bearing and a Method of Manufacturing Thereof

Abstract: A fluid dynamic bearing having a shaft (12) and a bearing sleeve (11) rotatably supported relative to each other. At least one of the shaft and the bearing sleeve is made of steel or stainless steel made of by weight C: 0.6˜1.20%; Si: 1.0 or less; Mn: 1.0% or less; Cr: 10.5˜18.0%; Mo: 1.0% or less; S.: 0.03% or less; and Fe. The dynamic pressure bearing surface (20) is formed by ridges (22) remaining in between multiple dynamic pressure grooves (21) formed by electrochemical machining.

Fixed-Geometry, Hydrodynamic Bearing with Enhanced Stability Characteristics

Abstract: This article presents the results of a successful bearing optimization study aimed at identifying a fixed-geometry, hydro-dynamic journal bearing that does not suffer from the low load instability typical of this class of bearings. This goal was met through optimization of a fairly simple objective function based on the rigid rotor whirl-speed ratio, using a constrained, nonlinear algorithm based on sequential quadratic programming. In the interests of reducing computational time, a two-dimensional isoviscous formulation of the Reynolds equation was used for this work. The equation was solved using a finite element approach. This article includes a discussion of the optimization approach, the finite element solution approach, the resulting bearing design, and its performance characteristics. It concludes with an application example comparing the optimized bearing's predicted performance to a tilting-pad bearing's predicted performance for a centrifugal compressor-like rotor. The mismatch between shaft and...

Piston pin : Wear and rotating motion

Abstract: In new engines, running conditions for piston pin bushes have become very severe due to combustion pressure and temperature increase Moreover, the lead removal from the bush material has strongly reduced the capability of the antifriction material to accept asperity contacts, geometrical defects or edge loading Today, it is usual that wear and seizure occur in the piston pin bushes during the first steps of engine development In order to propose basic design recommendations avoiding damage, during the early steps of engine development, it is necessary to have quick numerical simulations In these calculations, the mixed lubrication in the piston pin bearings must be taken into account To obtain a simple realistic tool, a refined contact model is implemented in a simple hydrodynamic lubrication program Then, the general behaviour of the piston pin is described before focusing on the combustion cycle phases when damage may occur The oil film thickness variations during cycle are described and show what the critical phases are Several parameters like pin diameter, temperature, pressure-viscosity coefficient have been investigated in order to understand their influence To have an efficient wear modelling a special emphasis is put on the description of asperity contacts in order to built a wear model for bearings located on the piston pin In this wear model, the surface topography parameters are taken into account in order to have a realistic approach and to identify the optimal roughness parameters

Finite element modal analysis of a rotating disk–spindle system in a HDD with hydrodynamic bearings considering the flexibility of a complicated supporting structure

Abstract: This paper presents a method to analyze the free vibration of a rotating disk–spindle system in a HDD with hydrodynamic bearings (HDBs) considering the flexibility of a complicated base structure by using finite element method. Finite element equations of each component of a HDD spindle system from the spinning flexible disk to the flexible base plate are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between the sleeve and hydrodynamic bearings to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. The validity of the proposed method is verified by comparing the calculated damped natural frequencies and modes with the experimental results. This research also shows that the supporting structure which includes the stator, housing and base plate plays an important role in determining the natural frequencies and mode shapes of a HDD spindle system

Frictionless compression testing using load-applying platens made from porous graphite aerostatic bearings

Abstract: In compression testing of soft materials at high strains, friction between a sample and the load-applying platens induces a differential lateral expansion that is visually evident as barreling. Barreling reduces the accuracy of the tests as a means of establishing accurate material properties. Current techniques for reducing friction, which involve liquid squeeze film lubrication, may not achieve true frictionless interfaces, are messy, and may adversely affect some samples. This article examines the use of porous graphite aerostatic bearings as a frictionless testing interface. The physics of a soft material under compressive loading by porous air bearings is investigated with simple finite element analysis and air flow models. An aerostatic bearing assembly is also constructed and compared to other friction reduction techniques. The results of these experiments indicate that there are benefits to using air bearings as they are clean, chemically inert, extremely stiff, reduce friction to levels comparabl...