Showing papers on "Fluid bearing published in 1998"

Tilting-Pad Journal Bearings With Electronic Radial Oil Injection

Abstract: This paper gives a theoretical treatment of the problem of journal bearings modeling connected to electronic oil injection into the bearing gap. The feasibility of influencing the static behavior of hydrodynamic forces by means of such oil injection is investigated. The lubricant is injected into the bearing gap by two mechanisms of lubrication. the conventional hydrodynamic lubrication and through orifices distributed along the bearing surface (active lubrication in the radial direction). By controlling the pressure of the oil injection, it is possible to get large variations in the active hydrodynamic forces; such effects could be useful for reducing vibrations in rotating machines.

A New Foil Air Bearing Test Rig for Use to 700°C and 70,000 rpm

Abstract: A new test rig has been developed for evaluating foil air bearings at high temperatures and speeds. These bearings are self-acting hydrodynamic air bearings which have been successfully applied to a variety of turbomachinery operating up to 650°C. This unique test rig is capable of measuring bearing torque during start-up, shutdown and high speed operation. Load capacity and general performance characteristics, such as durability, can be measured at temperatures to 700°C and speeds to 70,000 rpm. This paper describes the new test rig and demonstrates its capabilities through the preliminary characterization of several bearings. The bearing performance data from this facility can be used to develop advanced turbomachinery incorporating high temperature oil-free air bearing technology. Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 9–12, 1997

Centrifugal capillary seal for use with fluid dynamic bearings

Abstract: An improved capillary seal for use with a hydrodynamic bearing is disclosed, which provides a stronger or stiffer seal for a fluid dynamic bearing motor which is open at both ends, and is used with top cover attached motors utilizing fluid dynamic bearings. The design of the capillary seal uses centrifuigal force to actively push the oil back into the FDB while it is spinning, combined with the capillary tension which holds oil in the FDB during stationary periods. Also, the seal design comprises two walls which converge toward an apex near an adjacent fluid dynamic bearing. This design allows air, trapped within the seal and the associated FDB, to be expelled, eliminating air bubbles from the fluid dynamic bearing.

In-hub spindle motor with separate fluid dynamic bearings

Abstract: A hydrodynamic bearing system where the bearing includes a shaft and two independent bearings, comprising a top cone or bi-sphere and a bottom cone or bi-sphere separated by a segment of the shaft. The bearing includes a hub supported bearing element rotating around the shaft and the shaft supported top cone and bottom cone; complementary surfaces of said bearing element and said cone define a narrow gap between the bearing support element for the bearing fluid. Sealing plates or seal elements define a fluid gap with a radially extending face of the cone; a gap also exists between an interior surface portion of each cone and the shaft. These gaps are connected so that separate flow paths are established, one around the top cone or bi-sphere and one around the bottom cone or bi-sphere. By providing two independent bearings, the stator can be mounted to the shaft, facing magnets supported on the hub to form an in-hub motor. When the load or RPM changes, the fluid pressure or movement in each bearing may change but the function of the bearing and its ability to provide stiffness and stability to the system will not be lessened.

Use of computational fluid dynamics in hydrodynamic lubrication

Abstract: This paper demonstrates the suitability of using computational fluid dynamics software for solving steady state hydrodynamic lubrication problems pertaining to slider bearings, step bearings, journal bearings and squeeze-film dampers under conditions of constant unidirectional or rotating loading. The relevance of the inertia and viscous terms which are neglected in the derivation of the Reynolds equation are briefly investigated for the above bearing and damper configurations and it is shown that the neglected viscous terms have negligible effect whereas the inertia effect predictions agree reasonably well with those reported in the literature.

Bearing arrangement for air cycle machine

Abstract: A journal bearing designed for use with a rotatable shaft of an air cycle machine is disclosed. The bearing includes a journal bearing housing (14), air bearings (16a, 16b) for facilitating rotation of the shaft, and a journal bearing shell (12) positioned in the housing.

Asymmetric sealing means for fluid dynamic bearings

Abstract: An improved capillary seal for use with a hydrodynamic bearing is disclosed, which provides a stronger or stiffer seal for a fluid dynamic bearing motor which is open at both ends, and is used with top cover attached motors utilizing fluid dynamic bearings. The design for the seal system actively pushes the oil back into the FDB while it is spinning, combined with the capillary tension which holds oil in the FDB during stationary periods, and allows air, trapped within the seal and the associated FDB, to be expelled, eliminating air bubbles from the fluid dynamic bearing.

Rotodynamic pump with non-circular hydrodynamic bearing journal

Abstract: A blood pump (10) incorporates a blood lubricated journal bearing (82) that is characterized by a non-circular geometry (150). In one embodiment, the stationary bearing element, or stator, of the bearing is provided with a semi-elliptical shaped outer surface in an area opposite the load bearing film (104). The journal bearing configuration ensures that the blood flow therethrough is adequate, that the integrity of the blood is preserved and that bearing stability is maintained.

Fluid bearing operable in a vacuum region

Abstract: A fluid bearing suitable for use in a vacuum region comprises a fluid passageway for introducing a fluid into the bearing, a pump-out slot for evacuating the fluid from the bearing, and a bearing seal disposed along a periphery of the bearing to restrict fluid from escaping from the bearing into the vacuum region. The bearing seal comprises a bridge structure including a first base, a second base, a transverse member fixed at one end to the first base and movably disposed in a slot defined by the second base, and a sealing sheet extending from the transverse member between the first and second bases. The sealing sheet forms a compliant mechanical wall around the periphery of the bearing. The seal further includes an adjustable spring force element which exerts a force on the sealing sheet to ensure marginal contact with a bearing support surface to form a low-frictional seal. The sealing sheet confines the fluid which escapes outside of the pump-out slots to within the perimeter of the wall formed by the sealing sheet. The seal allows for movement of the air bearing relative to the bearing support surface and is suitable for use with an XY wafer or reticle stage. The air bearing and its seal may be adapted as a journal shaft-type bearing.

Rotational assembly for disc drive device having small runout and reduced axial displacement

Abstract: A disc drive device includes a rotational assembly which is adapted to mount a disc thereon and is rotatably driven by a motor. The rotational assembly is rotatably supported on a support assembly by a radial hydrodynamic fluid bearing and a thrust bearing. An axial load is applied to the thrust bearing by a magnetic attractive force of up to 30N and is greater than a dead weight of the rotational assembly.

Spindle motor with hybrid air/oil hydrodynamic bearing

Abstract: The present disclosure relates to a spindle motor including a shaft having an outer circumferential surface. The spindle motor also includes a thrust plate fixedly connected to the shaft. The thrust plate projects radially outward from the outer circumferential surface of the shaft and includes top and bottom surfaces. The spindle motor also includes a hub assembly mounted on the shaft. The hub assembly is adapted for mounting a storage disk. The spindle motor further includes a liquid hydrodynamic bearing and an aerodynamic bearing. The liquid hydrodynamic bearing is formed along the top and bottom surfaces of the thrust plate and is adapted for transferring loads in an axial direction relative to the shaft. The aerodynamic bearing is formed along a portion of the hub assembly and is adapted for transferring loads in a radial direction relative to the shaft.

Apparatus and method for performing end point detection on a linear planarization tool

Abstract: A technique for utilizing a sensor to monitor fluid pressure from a fluid bearing located under a polishing pad to detect a polishing end point. A sensor is located at the leading edge of a fluid bearing of a linear polisher, which is utilized to perform chemical-mechanical polishing on a semiconductor wafer. The sensor monitors the fluid pressure to detect a change in the fluid pressure during polishing, which change corresponds to a change in the shear force when the polishing transitions from one material layer to the next.

High stability spin stand platform

Abstract: Spin stand platform having split axes. The platform includes an air bearing spindle stage supporting a test disk and constrained for motion in a plane on a surface along a first axis. A micropositioning stage air bearing is provided which is constrained for motion in the plane on the surface along a second axis orthogonal to the first axis and the micropositioning stage is adapted to support a read head element under test. First and second acuators move the stages to desired locations. At the desired location, apparatus removes air from the air bearings to lock-down the stages to the surface at the desired locations. It is preferred that the air bearings be vacuum preloaded and that linear motors be used to move the stages.

A Nonlinear Dynamic Model With Confidence Bounds for Hydrodynamic Bearings

Abstract: In conventional rotordynamic modeling, hydrodynamic bearings are often characterized by a set of linear stiffness and damping coefficients obtained from a first-order Taylor series expansion of bearing reactions. Theoretically. these coefficients are only valid for small amplitude motion about an equilibrium position. In this paper, a nonlinear dynamic model that overcomes the small amplitude assumption in the conventional linear analysis is described, By including higher-order terms in the bearing reaction expansion, nonlinearity in the oil film forces for large amplitude motion can be captured and represented by a set of nonlinear stiffness and damping coefficients. These coefficients are functions of static bearing displacement. A finite difference approach is described and is used to solve for these coefficients. The stated model is applied to a conventional slider bearing and a mechanical smart slider bearing that experiences large variations in load. Error assessment is performed numerically on the higher-order solutions to determine an acceptable displacement bound for the higher order coefficients.

Grooved pumping seal

Abstract: An improved seal for a hydrodynamic bearing which aids in making the bearing less sensitive to changes in load and rotational speed, which is especially useful in hydrodynamic bearing motor in which the bearing is open at both the upper and lower ends. Additionally, a hydrodynamic bearing open at both ends in which the balance of fluid flow or pressure within the total system is maintained, and a seal usable to make a hydrodynamic bearing which is as stiff or stiffer than known standard spindle motors with hydrodynamic bearings which are supported only at one end. Also, a pumping seal useful in a hydrodynamic bearing design to maintain balanced internal fluid pressures during operation to minimize the likelihood of any lubricating fluid being lost during operation is disclosed.

Optical rotary encoder

Abstract: An optical rotary encoder is provided using a fluid bearing (6,7), which is space-saving, holds down costs for the high-precision processing of components, and has excellent maintainability A rotary disk (10) is fixed to a disk holder (5) and is accommodated in a cylindrical case (20) together with a fluid bearing mechanism (6,7) and an optical detection unit (4) The optical detection unit (4) and the fluid bearing mechanism (6,7) provide a static system with the cylindrical case (20), which maintains a stationary state even if a rotary shaft (1) is rotated, and are mounted on static system mounting portions (2,3) with the cylindrical case (20) The disk holder (5) and the rotary disk (10) are fitted on the rotary shaft (1) Compressed air is sprayed onto both sides of the rotary disk (10) through a compressed air flow path (6) and a compressed air nozzle (7), to thereby restrict displacement of the disk (10) in a direction parallel to the rotary shaft (1) The compressed air is also sprayed through the compressed air flow path (6) onto the outer circumference of the disk holder (5), to thereby restrict displacement of the disk (10) in a direction perpendicular to the rotary shaft (1) As an alternative to air, it is also possible to use helium or oil as fluid in the fluid bearing (6,7)

Mechanical seals enhanced with microstructures

Abstract: Properties of mechanical bearings and mechanical seals can be significantly improved by covering the load-bearing surfaces with fields of high aspect ratio microstructures (HARMs), such as microchannels or microposts. The HARMs can substantially enhance heat transfer capability and lubricant flow. The present invention uses microstructures and micro-channels manufactured by a modified LIGA process to enhance the performance of load bearing surfaces. Benefits include reduced operating temperatures, precise metering of lubricant flow to all affected surfaces, increased reliability, increased life, higher maximum rotational speed, and the ability of the seal or bearing to run "dry," that is, without periodic re-application of lubricant. The invention may be used with a variety of bearings and mechanical seals, including for example ball bearings, roller bearings, journal bearings, air bearings, magnetic bearings, single mechanical seals, double mechanical seals, tandem mechanical seals, bellows, pusher mechanical seals, and all types of rotating and reciprocating machines. Improved cooling jackets are also disclosed, for use with bearings, seals, or other applications.

Dynamic pressure fluid bearing device and motor equipped with this device

Abstract: PROBLEM TO BE SOLVED: To provide a dynamic pressure fluid bearing device which can improve the sealing effect of a lubricating fluid and in which a lubricating fluid can be recovered even when the lubricating fluid is scattered and a motor provided with the bearing device. SOLUTION: A dynamic pressure fluid bearing device 11 is provided with a shaft member 24 having a shaft section 28 and a discoid flange section 32, a sleeve member 26 which can rotate relatively to the shaft member 24, and a lubricating fluid 62 filling up the gap between the members 26 and 24. Radial dynamic pressure bearing means 52 and 54 are installed to the shaft section 28 of the member 24 and a thrust dynamic pressure bearing means 58 is provided on one surface of the flange section of the member 24. In addition, the internal surface of a cap member 44 facing the other surface of the flange section 32 is tapered 60 over a relatively wide extent so that the clearance between the other surface of the flange section 32 and the internal surface of the cap member 44 can become narrower as going to the outside in the radial direction and the sealing boundary of the fluid 62 is positioned on the taper 60. Therefore, a force which is balanced with the thrust force generated by means of a thrust dynamic pressure bearing means 56 acts on the shaft member 24 in the direction opposite to the thrust force.

Polishing method using a hydrostatic fluid bearing support having fluctuating fluid flow

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.

Modeling Aspects of a Rate-Controlled Seizure in an Unloaded Journal Bearing

Abstract: Thermally induced seizure can lead to a rapid catastrophic bearing failure. An analytical model was developed to study this phenomenon in an unloaded journal bearing. The model consisted of two concentric cylinders containing lubricant in which the inner one rotates at a specified rpm and the outer cylinder is stationary. The appropriate governing equations and numerical solution schemes for treating the transient heat transfer in the fluid and the bounding solids are presented. Computations indicate that, depending on the operating conditions and thermomechanical properties, a bearing can rapidly lose its operating clearance. A parametric study with an extensive amount of numerical results is presented. It is shown that the clearance loss variation with time is initially linear up to a point after which its rate of reduction becomes much greater. Closely related to this non-linearity is the behavior of the friction torque which sharply rises before the clearance totally vanishes. The effect of thermomech...

Viscosity compensation by spindle motor pre-heating

Abstract: A disk drive system includes a base, a disk stack rotatably attached to the base, and an actuator assembly movably attached to the base. The disk stack is rotatably attached to the housing or the base using a hydrodynamic bearing. The disks are actually mounted or attached to a hub. An electric motor is formed inside the hub. Current is passed through the windings of an electric motor to rotate the hub. The windings are located near the bearing surface of the hydrodynamic bearings. Before applying a current which will start the rotation of the hub, a current is passed through the windings or coil of the electric motor to heat the lubricating fluid used as part of the hydrodynamic bearing. By heating the lubricating fluid, the start torque required to begin the rotation of the hub according to the start profile is reduced. The length of time for application of current at a level which heats the bearing surface and the lubricating fluid at the bearing surface may be controlled by a feedback control loop or may merely be a selected time which does not vary from disk drive to disk drive. Various indicators of the viscosity of the lubricant can be used to monitor the viscosity, if a feedback control loop is used. An adaptive program can also be used based on parameters such as temperature, sensing of winding current, and voltage. The current applied before startup can be alternating current or direct current.

Stable blood lubricated hydrodynamic journal bearing with magnetic loading.

Abstract: The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) is distinguished by the use of a special hydrodynamic journal bearing to support the rotating assembly of the blood pump. In a permanently implanted blood pump, this bearing's characteristics of long life and high reliability are of paramount importance. In addition, this bearing's inherent self-pumping flow and the axial through flow caused by an imposed end-to-end pressure difference provides good washing, thus guarding against deposition. The basic computer analysis and preliminary testing results of this bearing were previously presented. This article reports the ongoing studies (both analytic and in vitro tests) on this innovative bearing as a component of the IVAS in general, with particular emphasis on its stable operating characteristics and reliability. The absence of vibration attributable to hydrodynamic instabilities related to the thick fluid film are both calculated and demonstrated during testing. A stable operating center of the rotor is shown to be inherent under magnetic side loads and resulting hydrodynamic bearing forces. A low shear as a result of large fluid-film thicknesses has been calculated, and low hemolysis has been shown by in vitro testing. Several unique design features of the bearing are believed to be responsible for this high level of performance.

Recording and/or reproducing apparatus having rotary scanning drum supported by a bearing having contacting bearing surfaces which provide electrical grounding

Abstract: An apparatus having a read/write head for reading and/or writing information on an information carrier which may be in the form of a tape or disc. The head is mounted on a drum which is supported on a shaft which axially rotates the drum so as to move the head relative to the information carrier, which in the case of a tape winds around the drum. The drum is supported in the axial direction by a thrust bearing and in the radial direction by fluid bearings (25) and (26). The thrust bearing has adjoining surfaces of which at least one is made of cemented tungsten carbine, the other possibly being of steel. Thus, there is low friction and low wear. During operation of the apparatus the bearing surfaces remain in contact, thereby forming an electrical coupling to a grounding frame of the apparatus so as to limit static charging of the rotating drum.

On the Performance of Hybrid Foil-Magnetic Bearings

Abstract: Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each others weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both.To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed.Copyright © 1998 by ASME