Showing papers on "Fluid bearing published in 1994"

A Test Apparatus and Facility to Identify the Rotordynamic Coefficients of High-Speed Hydrostatic Bearings

Abstract: A facility and apparatus are described which determine stiffness, damping, and added-mass rotordynamic coefficients plus steady-state operating characteristics of high speed hydrostatic journal bearings. The apparatus has a current top speed of 29,800 rpm with a bearing diameter of 7.62 cm (3 in.). Purified warm water, 55 C (130 F), is used as a test fluid to achieve elevated Reynolds numbers during operation. The test-fluid pump yields a bearing maximum inlet pressure of 6.9 Mpa (1000 psi). Static load on the bearing is independently controlled and measured. Orthogonally mounted external shakers are used to excite the test stator in the direction of, and perpendicular to, the static load. The apparatus can independently calculate all rotordynamic coefficients at a given operating condition.

Wafer polishing machine with fluid bearings

Abstract: A semi-conductor wafer polishing machine having a polishing pad assembly and a wafer holder includes a support positioned adjacent the polishing pad assembly. The support includes multiple fluid bearings that support the polishing pad assembly on the support. These fluid bearings are arranged concentrically to provide concentric regions of support for the polishing pad assembly, and each fluid bearing is coupled to a respective source of pressurized fluid at a respective pressure.

Hydrostatic and active control movable pad bearing

Abstract: A one piece hydrodynamic bearing which can include hydrostatic support features. The pads are supported on a single thin web for pivoting on a support structure which can include one or more beam-like members. The bearings may have hydrostatic and active control attributes and is very attractive in cryogenic applications where it is very difficult to prevent leakage in conventional hydrostatic tilt pad bearings. The hydrostatic feed through the post eliminates this problem completely and prevents the fretting at the pivots common with conventional tilt pad bearings. A cavity provided under a pad support membrane can be used as an active control device. The pressure can cause the bearing set or assembly clearance to be reduced thus providing better damping and centering capability. The preload in the pad can be actively controlled in this manner. The pad has a limiting device to prevent a negative pre-load condition from occurring. This active control of bearing clearance can allow bearings to operate at large spreads in temperatures.

Experimental Test Results for Four High-Speed, High-Pressure, Orifice-Compensated Hybrid Bearings

Abstract: In this study, four hybrid bearings having different geometric configurations were experimentally tested for their static and dynamic characteristics, including flowrate, load capacity, rotordynamic coefficients, and whirl frequency ratio. The four bearings included a square-recess, smooth-land, radial-orifice bearing (baseline), a circular-recess bearing, a triangular-recess bearing, and an angled-orifice bearing. Each bearing had the same orifice diameter rather than the same pressure ratio. Unique to these test results is the measurement of the added mass terms, which became significant in the present tests because of high operating Reynolds numbers. Comparisons of the results were made between bearings to determine which bearing had the best performance

A Study of the Thermohydrodynamic Performance of Steadily Loaded Journal Bearings

Abstract: A comprehensive thermohydrodynamic (THD) analysis of steadily loaded journal bearings has been developed that includes mass conserving cavitation, full solution of the 3-D energy equation in the oil film, heat conduction in the bushing and journal, mixing of hot circulating oil with fresh supply oil and solution of the inverse problem (given the load, find the film thickness). The temperature distribution in the oil film and bushing is found using a coupled approach where the same 3-D energy equation is solved in both the oil film and bushing. With this approach the steady-state problem can be solved without iterations between the thermal solutions in the oil film and the bushing, thereby allowing ready analysis of multilayer bushings. Predictions of the analysis compared very well with measurements reported by Dowson et al. (1). A thermohydro-dynamic study of bearing performance as a function of clearance for a typical automotive bearing revealed that there is an optimum clearance that gives the largest ...

Single plate hydrodynamic bearing with self-balancing fluid level and fluid circulation

Abstract: The present invention includes four sections or partitions: two thrust bearings which are formed by the sides of a grooved thrust plate and corresponding countersurfaces, the thrust bearings designed to cause fluid flow in a single direction up around the rotating thrust plate and upward along the surface of a rotating journal, and two journal bearings formed side-by-side on the journal formed between a rotating shaft and a bushing with multiple spiral-grooved sections being formed on the rotating shaft or in the stationary bushing. The two journal bearings are separated by a circumferential groove in the shaft which is connected by a radial bore to a hollow reservoir in the shaft for providing fluid to the journal bearing and the thrust bearing. By providing this bore and a second bore located near to the thrust bearing, the boundary conditions for the combined journal bearings and thrust bearings are fixed and a stable rotating shaft is achieved.

Fluid retention principles for hydrodynamic bearings

Abstract: A hydrodynamic bearing incorporates a flexible membrane at one end of the fluid gap in the hydrodynamic bearing. If voids exist in the fluid, and if changes in the size of these voids or bubbles occur with changes in temperature or pressure in which the disc drive is being used, then the volume of the fluid will change, and increase relative to the change in size of the volume of the surrounding physical part. The flexible membrane will yield to the increased pressure of the increasing volume of the fluid. The membrane essentially acts as a spring whose spring force is overcome by the pressure created by or accompanying a increase in volume of the fluid. As this happens, the spring force of the membrane is overcome, the membrane relaxes and forms a bladder, effectively increasing the volume in which the lubricating fluid is contained, and preventing its escape or being forced out of the inner region of the bearing. In this way, the fluid remains in the bearing and will not enter the surrounding atmosphere, nor will it be lost from the journal bearing region so that the hydrodynamic bearing is not as effective, when the temperature decreases or the pressure drops.

A study on the characteristics of externally pressurized air bearings

Abstract: In this study the direct numerical method is applied to solve the perturbed Reynolds' equation. To solve it the perturbed dimensionless mass flow rate is used as the boundary condition under the inherently compensated restrictor. The dynamic characteristics of a rotor supported in the externally pressurized air bearings, such as stiffness and damping coefficients, are analyzed, and as a result the orbit of the journal center due to rotating unbalance force is calculated. The diameter of the orbit has been experimentally determined based on the three-point method. The maximum difference between the measured and calculated diameters was less than 5%.

Integrated hydrodynamic bearing/motor assembly

Abstract: A spindle and hub assembly in a disk drive having an integrated motor including a housing having a cylindrical sleeve and two end flanges, the cylindrical sleeve and the upper end flange being one piece and forming the hub and the lower end flange being pressed into the hub and a shaft being rotatably supported in the end flanges by means of hydrodynamic bearings, where the hydrodynamic bearings have conical bearing surfaces converging towards the interior of the housing, whereby a high precision and low cost spindle and hub assembly is provided.

Effect of viscous dissipation on the lubrication characteristics of micropolar fluids

Abstract: Thermohydrodynamic solutions are presented for a finite journal bearing lubricated with micropolar fluid. Comparison with isothermal results, assuming that viscosity remains at the inlet temperature, is also given. Results indicate the heat generation due to viscous dissipation plays an important role on the load-carrying of a journal bearing lubricated with micropolar fluids.

Single plate hydrodynamic bearing with self-balancing fluid level

Abstract: A thrust plate with grooved surfaces within a hydrodynamic bearing establishes pressure gradients which cause the lubricating fluid for the bearing to reliably remain within the region of the hydrodynamic bearing, with the pressure gradient imposed on the fluid causing the fluid to flow toward the center of the bearing rather than to be caused to be forced outward toward the far end of the bearing which could potentially result in a leakage of the fluid.

Sinusoidal grooving pattern for grooved journal bearing

Abstract: A bearing having two surfaces (60, 72) rotatable with respect to each other, a lubrication medium located in a gap between the two surfaces during rotation of the bearing and a sinusoidal groove pattern (20) formed on one of the two surfaces to distribute the lubrication medium over the surface of the bearing and create a pressure distribution in the bearing to create a stiff hydrodynamic bearing.

Hydrodynamic fluid bearing with liquid-radial bearing and gas-thrust bearing

Abstract: A bearing device suitable for a spindle motor, which comprises a base, a spindle stood on a central portion of the base, a radial cylindrical member (4) fixed on the spindle, a pair of thrust plates (3) secured to both end surfaces of the radial cylindrical member, and a radial sleeve (6) rotatably supported by the thrust plates (3) and the radial sleeve (6), wherein a radial hydrodynamic bearing is formed by the radial cylindrical member (4) and the radial sleeve (6), thrust hydrodynamic bearings are formed by both end portions of the radial sleeve (6) and the thrust plates (3), a gas is employed as a fluid for generating dynamic pressure in the thrust hydrodynamic bearings, the radial bearing has a minute clearance, a chamfer portion is provided on the outer periphery of each end of the radial cylindrical member (4), and another chamfer portion is provided on the inner periphery of each end of the radial sleeve (6), thereby providing an air gap (13) at each axial end of the radial hydrodynamic bearing, which is surrounded by these chamfer portions and one thrust plate (3), a lubricating liquid is employed as a fluid for generating dynamic pressure in the radial hydrodynamic bearing, small holes (8) for collecting the lubricating liquid are formed in the outer peripheral surface of the radial cylindrical member (4), and lubricating liquid is sealed in the bearing clearance of the radial hydrodynamic bearing by virtue of the presence of the air gaps (13).

Wafer polishing machine with fluid bearings and drive systems

Abstract: A semi-conductor wafer polishing machine having a polishing pad assembly and a wafer holder includes a support positioned adjacent the polishing pad assembly. This support has at least one fluid inlet connectable to a source of fluid at a higher pressure, at least one fluid outlet connectable to a fluid drain at a lower pressure, and at least one bearing surface over which fluid flows from the source to the drain. The polishing pad is supported by the fluid over the bearing surface for low-friction movement with respect to the support. Similar fluid bearings can be used in the wafer holder. An array of generally parallel grooves is provided on a belt support surface to reduce hydroplaning of a polishing belt. A turbine drive system rotates a wafer chuck in a wafer holder.

Apparatus for empirical determination of dynamic friction

Abstract: An apparatus for measuring dynamic friction in a lubricated journal bearing is described. This apparatus has been designed, constructed and used to measure friction in the presence of sinusoidally-varying velocity at various frequencies. Experimental results tend to confirm theoretical predictions which are based on the hydrodynamic lubrication theory.

Effect of load direction, preload, clearance ratio, and oil flow on the performance of a 200 mm journal pad bearing

Abstract: Journal pad bearings are widely used in industry, particularly in high-speed applications. Previous experimental work with bearings of this sort has tended to be fragmented and mainly confined to smaller and relatively lightly loaded bearings. The purpose of this paper is to present temperature measurements and derived values of power loss from a new, extensive experimental program involving a 200 mm diameter journal pad bearing, operating at speeds up to 105 m/s and loaded at specific pressures up to 4.14 MPa. The program was designed to isolate some important design parameters and determine their effect on bearing temperatures and energy consumption. Bearing clearance, journal pad preload, the direction of the applied load, and the impact of radically reducing the amount of lubricant supplied to the bearing are all examined. In particular, it is found that load line direction has a substantial impact on maximum pad temperature. It is also shown that large reductions in the volume of oil supplied to the ...

Static Analysis of Flying Characteristics of the Head Slider by Using an Optimization Technique

Abstract: This paper suggests a method to predict the static solution for gas-lubricated slider bearings in a hard disk drive (HDD) by using an optimization technique. The modified Reynolds equation for the hydrodynamic lubrication theory under the slip condition is used to describe the compressible fluid flow within the gas bearing, and a factored implicit finite difference (FIFD) scheme is applied for pressure calculations. An optimization technique is employed to find the solution at which the forces and moments acting on the gas bearing are in a state of equilibrium

On the Theory of Quasi-Hydrodynamic Lubrication with Dry Powder: Application to Development of High-Speed Journal Bearings for Hostile Environments

Abstract: This paper describes a series of experiments aimed at the demonstration of the basic feasibility of developing a powder-lubricated, quasi-hydrodynamic (PLQH) journal bearing for high-temperature and hostile environments, where the use of liquid lubricants is impractical. A PLQH bearing has demonstrated operation at speeds to 2 × 10 6 DN (58,000 rpm), and it may be the only bearing capable of meeting the ever-demanding tribological goals of a solid lubrication scheme for extreme environments. The work described exceeds the current state of the art (1.5-million DN) in solid-lubricated ceramic rolling element bearing technology, and there is great promise for integrating this technology in outer space systems/mechanisms and in other hostile-environment applications. Experimental evidence shows that powder lubricant films behave much as fluid films do, whereby mechanisms are provided that lift and separate bearing surfaces and cause side leakage. These mechanisms reduce the friction coefficient and, consequently, the heat generated in the bearings, which drastically reduces wear of the tribo-materials. Further, bearing side leakage provides a significant mechanism for heat dissipation because it carries away most of the heat generated by shear, reducing the heat to the critical bearing surfaces (see Figure 1). Experimental parametric studies have delineated the hydrodynamic effects of powder lubrication (MoS 2 ) on bearing performance criteria, such as load, temperature, and power loss as a function of speed, including the effect of powder flow rate on bearing performance characteristics. Comparison with a liquid lubricant provides evidence for the continuum basis for the phenomenological unification of solid particulates and liquid.

An Introductory Guide to Industrial Tribology

Abstract: Friction and Boundary Lubrication: The nature of solid surfaces, Friction Boundary lubrication, Solid lubrication, Fretting Fluid Film Lubrication: Hydrostatic lubrication, Hydrodynamic lubrication, Elasto-hydrodynamic lubrication, Mixed lubrication, Squeeze films, Gas-film lubrication Lubricants: Properties required in lubricants, Mineral lubricating oils, Lubricating-oil additives, Grease, Synthetic lubricants, Solid lubricants Lubricants in Service: Change periods, Visual examination, Routine laboratory testing, Maintenance of lubricants in service Selection of Bearing Type: Selection of the basic bearing type, More detailed consideration in bearing selection, Plain bearing failures, Process fluid lubricated bearings Rolling Bearings: Designing with rolling bearings, Selection of rolling bearings, Lubrication of rolling bearings, Bearing 'equivalents', Rolling bearing failures Methods of Lubrication: Plain bearings, Oil circulation systems, Gears, Cylinders of reciprocating compressors Fire and Explosion Hazards with Mineral Lubricating Oils: Crankcase explosions Hydraulic system fires, Lagging fires, Air compressor fires and explosions, Explosions in high-pressure pneumatic systems Dynamic Seals: Sealing of liquids, Sealing of gases Wear: Wear mechanisms, Wear relationships, Wear in practice, Some generalizations.

Fluid bearing unit and manufactured method thereof

Abstract: A fluid bearing unit includes a shaft; a bearing; bearing fluid arranged between a shaft and a bearing which are rotatably engaged with each other so that they can be relatively rotated so as to generate dynamic pressure in the bearing fluid, wherein at least one of the bearing and the member for fixing the bearing unit is made of iron alloy having the volumetric magnetostriction of which acts to cancel the thermal expansion so as to become the coefficient of linear expansion thereof lower than that of the shaft.

Dynamic Force Response of Spherical Hydrostatic Journal Bearings for Cryogenic Applications

Abstract: Hydrostatic journal bearings are ideal elements to replace roller bearings as rotor support elements in cryogenic lurbomachinery. These bearings will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, and direct stiffness and damping force coefficients. The performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings are presented. These bearings allow tolerance for shaft misalignment without force degradation and are able to support axial loads, thus providing a design configuration which could be used efficiently on high-performance turbomachinery. Bulk-flow mass and momentum equations for the motion of a variable properties liquid on the thin film bearing lands are solved numerically. Predictions of load capacity and force coefficients for a six recess, spherical hydrostatic bearing in a liquid oxygen environment are presented. Fluid film axial forces and dynamic coefficients of a magnitude a...

Turbine having suspended rotor blades

Abstract: A high-efficiency turbine includes low-tensile-strength rotor blades capable of high-temperature operation (such as ceramic) which are mounted on fluid bearings between a continuous rim and a hub, the rim being connected via high-tensile-strength spokes through each blade to the hub. The fluid provides internal support to the blade structure and provides a bearing medium and force with which to maintain blade position under compression. One or more fluids may be employed as coolants in passages within the blade to establish an adequate temperature gradient between blade surface and the associated spoke to minimize spoke failure due to overheating.

Monitoring, materials, synthetic lubricants, and applications

Abstract: Monitoring and Maintenance Condition Monitoring Sensors and Systems, E. Venalainen Automotive Engine-Oil Condition Monitoring, D.J. Smolenski and S.E. Schwartz Diesel Engine Lube Analysis, J. Poley Rotating Machinery Vibration Testing, Condition Monitoring, and Predictive Maintenance, W.D. Marscher Filtration Rapid Determination of Remaining Useful Lubricant Life, R.E. Kauffman Materials Friction and Wear of Ceramics, S. Jahanmir and T.E. Fischer Plastics and Plastic Matrix Composites, W.E. Jamison Metal Matrix-Solid Lubricant Composites, P.K. Rohatgi, S. Ray, and Y. Liu Bonded Solid Film Lubricants, R.M. Gresham Synthetic Lubricants Aerospace Applications of Synthetic Fluids and Lubricants, C.E. Snyder, Jr. and L.J. Gschwender Industrial Applications, D.A. Lauer Automotive Applications, B.J. Beimesch Polyalphaolefins, R.L. Shubkin Dibasic Acid and Polyol Esters, J.M. Perez and E.E. Klaus Polyalkylene Glycols, W.L. Brown Phosphate Esters, M.P. Marino and D.G. Placek Perfluoroalkylpolyethers, T.W. Del Pesco Silicones, E.D. Brown Applications Tribology of Magnetic Storage Systems, B. Bhushan Computers and Office Machines, R.G. Bayer Refrigeration and Air Conditioning, G.D. Short Oil Mist Lubrication, D.M. Bornarth Tribology in High Speed Machining, R. Komanduri and D.G. Flom Bearing and Seals Hydrodynamic and Hydrostatic Seals, W. Shapiro Rolling Bearing Fatigue Life, C.A. Moyer and W.J. Derner Porous Metal Bearings, C. Cusano Self-Contained Bearing Lubrication: Rings, Disks, and Wicks, R.C. Elwell Water and Process Fluid Bearings, R.L. Orndorff, Jr. Gas Bearings, M. Khonsari, L.A. Matsch, and W. Shapiro Magnetic Bearings, P.E. Allaire, P. Allaire, E.H. Masleu, R.R. Humphris, C.R. Knospe, and D.W. Lewis Index.

A Study of the Mechanism of Lubrication in Porous Journal Bearings: Effects of Dimensionless Oil-Feed Pressure on Static Characteristics Under Hydrodynamic Lubrication Conditions

Abstract: The static characteristics of porous journal bearings under hydrodynamic lubrication conditions are theoretically investigated assuming that the oil is fed through their outside diameters under a small pressure. The angular extent of the oilfilm formed in the bearing clearance is numerically solved on the basis of the following postulate: when the oil film extent reaches steady state, the inflow of oil into the bearing clearance through the porous matrix due to the oil-feed pressure must make up for the oil leakage from the ends through the clearance gap and that into the porous matrix due to the hydrodynamic pressure in the film