Showing papers on "Fluid bearing published in 1995"

Wave journal bearing with compressible lubricant--Part 1: The wave bearing concept and a comparison to the plain circular bearing

Abstract: To improve hydrodynamic journal bearing steady-state and dynamic performance, a new bearing concept, the wave journal bearing, was developed at the author's lab. This concept features a waved inner bearing diameter. Compared to other alternative bearing geometries used to improve bearing performance such as spiral or herring-bone grooves, steps, etc., the wave bearing's design is relatively simple and allows the shaft to rotate in either direction. A three-wave bearing operating with a compressible lubricant, i.e., gas is analyzed using a numerical code. Its performance is compared to a plain (truly) circular bearing over a broad range of bearing working parameters, e.g., bearing numbers from 0.01 to 100.

Hydrodynamic bearing with controlled lubricant pressure distribution

Abstract: A rotating-shaft hydrodynamic bearing assembly adapted for use in a rotating disk data store. The bearing assembly combines a plurality of spaced-apart radial journal bearings with a two-faced axial thrust plate to provide stiffness against runout at high rotational velocities. Fluid pressure is controlled on both sides of every fluid dement by bounding all radial fluid bearing layers and the dual thrust bearing layers with circumferential undercuts coupled to ambient pressure through a plurality of fluid-filled passages in the rotating shaft. Outward-biased surface-relief patterns are disposed in both axial thrust bearing layers to increase hydrostatic pressure and prevent cavitation in the non-bearing thrust-plate peripheral layer. The fluid bearing layers are disposed in a continuous pressure-controlled fluid film sealed at both ends by surface tension, thereby eliminating sources of air-bubble entrapment. Control of air-bubble entrapment and cavitation eliminates both as sources of surface-tension seal leakage and blowout.

On the Adjusting of the Dynamic Coefficients of Tilting-Pad Journal Bearings

Abstract: This paper gives a theoretical and experimental contribution to the problem of active modification of the dynamic coefficients of tilting-pad journal bearings, aiming to increase the damping and stability of rotating systems. The theoretical studies for the calculation of the bearing coefficients are based on the fluid dynamics, specifically on the Reynolds equation, on the dynamics of multibody systems and on some concepts of the hydraulics. The experiments are carried out by means of a test rig specially designed for this investigation. The four pads of such a bearing are mounted on four flexible hydraulic chambers which are connected to a proportional valve. The chamber pressures are changed by means of the proportional valve, resulting in a displacement of the pads and a modification of the bearing gap. By changing the gap, one can adjust the dynamic coefficients of the bearing. With help of an experimental procedure for identifying the bearing coefficients, theoretical and experimental results are co...

Disk driving apparatus

Abstract: A disk driving apparatus solves such problems that the position of a rotor is unstable and likely to float, and the rotor is displaced when an excessive acceleration is applied thereto, so that a hydrodynamic bearing mechanism can be used. This apparatus uses a single surface opposing type mechanism in a thrust bearing of a motor. It has a device using a magnetic attraction force to stabilize the position of the rotor and various devices for limiting the amount of movement of the rotor, in which devices members which physically contact the rotor and lock in are provided. As a result, a thrust bearing mechanism can be formed by use of a single surface opposing type thrust bearing which is simple in construction. Advantages such as low height, simplicity in construction, low price, or low consumption of power can be obtained. In particular, the feature of low height is extremely advantageous when a hydrodynamic bearing is used in a thin type apparatus.

Theoretical and Experimental Comparisons for Rotordynamic Coefficients of a High-Speed, High-Pressure, Orifice-Compensated Hybrid Bearing

Abstract: Comparisons are presented between measurements and predictions for a 76.2 mm diameter, high-speed (24,600 rpm), high-pressure (7.0 MPa), hybrid bearings using warm (54°C) water as a test fluid. «Hybrid» refers to combined hydrostatic and hydrodynamic action. Test results are presented for an orifice-fed, square-recess configuration with five recesses. Data are provided for rotordynamic coefficients including direct and cross-coupled stiffness, direct damping, direct added-mass coefficients, and the whirl-frequency ratio. Experimental results are compared to predictions from an analysis by San Andres (1990a), which accounts for both temporal and convective acceleration terms in the fluid film. San Andres' development uses an orifice discharge coefficient to model the pressure drop from supply pressure to recess pressure. With experimentally determined discharge-coefficient values as input, good agreement is obtained between theary and experiment. However, predictions are sensitive to changes in the orifice discharge coefficients

Compact electric motor construction employing fluid bearings

Abstract: A compact electric motor construction employing fluid bearings for use in a disk drive apparatus includes a spindle having a shaft and a thrust plate and a hub assembly including a hub having an outer disk support portion with an inner thrust bearing surface located axially above the upper thrust bearing surface of the thrust plate. The hub also includes an inner sleeve which substantially surrounds the shaft and provides an air gap between its inner diameter and the outer diameter of the thrust plate. The air gap is vented to the interior of the motor cavity by vent passages. Transition grooves are provided on bearing surfaces adjacent all fluid seal zones for controlling the migration of bearing fluid in a radial direction and for providing a low fluid pressure region adjacent capillary seals at the ends of the shaft to contain the seal and prevent leakage.

Wave Journal Bearing with Compressible Lubricant—Part II: A Comparison of the Wave Bearing with a Wave-Groove Bearing and a Lobe Bearing

Abstract: To identify the potential advantages of the wave journal bearing, a three-wave journal bearing was compared to both a three-wave-groove bearing (a wave bearing with axial grooves that isolate each wave) and a three-lobe bearing. The lobe bearing's profile was selected to approximate the wave journal bearing's profile. The lubricant was assumed to be compressible (gas). The bearing number, A, was parameterized from 0.01 to 100, and the eccentricity ratio, e, was varied from 0 to 0.4. Data at bearing numbers 0.1, 1, and 50, and eccentricity ratios of 0.1 and 0.4, were selected as representative of the bearing performance. The calculated load capacity and the critical mass are presented for the three bearings. The wave bearing shows a better load capacity than the other bearings at any applied load and running regime. However, at high bearing numbers the lubricant compressibility effect is predominant and all three analyzed bearings show similar load capacity. The critical masses of the wave-groove and lobe ...

Wafer polishing machine

Abstract: A semi-conductor wafer polishing machine (10) having a polishing pad assembly (14), and a wafer holder (12) includes a support (24) positioned adjacent the polishing pad assembly (14). This support (24) has at least one fluid inlet (36) connectable to a source of fluid at a higher pressure, at least one fluid outlet (38) connectable to a fluid drain at a lower pressure, and at least one bearing surface (40) over which fluid flows from the source to the drain. The polishing pad (14) is supported by the fluid over the bearing surface (40) for low-friction movement with respect to the support (24). Similar fluid bearings can be used in the wafer holder (12). 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 (12).

Misalignment Effect on the Static and Dynamic Characteristics of Hydrodynamic Journal Bearings

Abstract: This paper solves the Reynolds equation by the finite difference method in a fixed coordinate system with the static load acted in the vertical direction. All static and dynamic characteristics (including load capacity, attitude angle, side flow, friction force, misaligned moments, and eight linear force coefficients) of a horizontally grooved bearing under different eccentricity and misalignment conditions are presented and compared with available experimental data. The effects of misalignment on all these bearing characteristics and on the stability of the rotor-bearing system are analyzed.

Disc drive with self-pressurizing fluid bearing and shaft-supporting-ball retaining element

Abstract: The present invention replaces the current spindle motor ball bearing system of a hard disc drive by a system comprising three separate elements, including a self-pressurizing journal bearing for establishing radial stiffness which comprises a rotating shaft and sleeve with air or other fluid therebetween. A chevron or herringbone pattern is established on the sleeve or shaft to establish a self-pressurizing hydrodynamic bearing which maintains the stability of the system while providing for very simple manufacturing of the system. Additionally, a thrust bearing is defined based on the air pressure build-up between the housing for the disc stack and the disc stack itself. The term "integrated air-bearing" is used to name this thrust bearing because it is built up with components such as discs and housing which exist in any typical hard disc assembly. The integrated air-bearing may be sufficiently established by building up the bottom surface of the housing or the base of the housing to within a very close distance of the lower surface of the disc; preferably, both the top surface of the top disc and bottom surface of the bottom disc are located close to pads, or other configurations are built up to define a narrow gap between the top and bottom surfaces of the disc stack and the housing. Third, an axial elastic thrust bearing defines the axial position of the disc stack at rests and avoiding contact between the surfaces forming the integrated air-bearing (in other terms, disc and housing). This elastic thrust bearing comprises a ball fixed to the shaft that rest against an elastic shield fixed to the end sleeve of the journal bearing or the base of the disc drive. This bearing defines the axial position of the disc stack.

Hydrodynamic bearing for spindle motor having high inertial load

Abstract: A self-contained hydrodynamic bearing unit includes a shaft having a threaded axial opening at one end thereof and a shaft shoulder adjacent the opening and perpendicular with a longitudinal axis of the shaft, a sleeve defining an opening for receiving the shaft for relative rotation, a pair of longitudinally spaced-apart radial hydrodynamic journal bearings defined between the shaft and the sleeve, a shaft-bolt including a threaded end region for mating with the threaded axial opening of the shaft and defining a bolt shoulder, an annular thrust plate having two parallel radial faces and adapted to fit upon the shaft-bolt for mounting between the shaft shoulder and the shaft bolt shoulder when the shaft-bolt is mated with the threaded axial opening of the shaft, the sleeve defining a radial thrust bearing surface portion extending radially outwardly at one end and positioned to confront one radial face of the thrust plate, an annular thrust bushing mounted to the sleeve and defining a radial thrust bearing surface portion confronting the other radial face of the thrust plate, the annular thrust plate defining two axial hydrodynamic thrust bearings respectively with the radial thrust bearing surface portion of the sleeve and the radial thrust bearing surface portion of the annular thrust bushing and a hydrodynamic thrust bearing lubricant reservoir between the two axial hydrodynamic thrust bearings and between a cylindrical face of the thrust plate and a facing cylindrical wall of the sleeve, and a hydrodynamic bearing lubricant in the bearing unit and at the pair of hydrodynamic journal bearings and at the two axial hydrodynamic thrust bearings and in the hydrodynamic bearing lubricant reservoir.

Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings

Abstract: The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust bearing and the action of thrust bearing on system dynamics. It is shown that thrust bearing changes the load distribution of journal bearings and the static deflection of the rotor and delays the instability of the system considerably in lateral shaft vibration.

Non-linear hydrodynamic bearing

Abstract: Non-axially-cylindrical journal and bearing assembly operates with hydrodynamic lubrication and has high load capability.

Stability of Rough Journal Bearings Using Nonlinear Transient Method

Abstract: The stability of rigid rotors supported on finite oil rough journal bearings has been investigated using nonlinear transient method. The effect of various surface roughness parameters, viz., composite surface roughness, roughness orientation pattern, variance ratio on the stability is presented in the form of journal center trajectories. Although the stability is affected marginally with the increase in composite roughness, the variation is quite significant when the shear flow factor comes into the picture.

Fluid bearing pad arrangement for liquid ring pump systems

Abstract: Liquid ring pumps with rotating canisters are supported by at least one radial fluid bearing pad. The bearing fluid is either a gas or a liquid. The radial fluid bearing pads can be of either the hydrodynamic or hydrostatic type. Holes in each bearing pad are used to introduce bearing fluid to the clearance between the rotating canister and the housing of the pump. Each radial bearing pad can be mounted to the housing using a ball joint or a bladder. Access ports formed in the housing provide access to the radial bearing pads. Axial fluid bearings are mounted to the housing using shims or threaded bolts so that the axial position of the axial bearings can be adjusted.

Disk drive with fluid bearing, bearing plate and disk-moving mechanism

Abstract: A disk drive apparatus having a fluid bearing, an enclosure, a fixed shaft, a hub, a working fluid, spiral grooves, a disk, a head, and an axial-gap three-phase brushless motor. The shaft has two ends and a peripheral surface. The hub has a first inner surface opposing one end of the shaft and a second inner surface surrounding the peripheral surface of the shaft, and is designed to float with respect to the shaft by virtue of a fluid pressure. The working fluid is provided in a gap between the one end of the shaft and peripheral surface of the shaft, on the one hand, and the inner surfaces of a cup-shaped member, on the other hand. The spiral grooves are formed in at least one of the peripheral surface of the shaft and the first inner surface of the cup-shaped member. A bearing plate lies opposite the disk at a distance while stationary. When the disk moves, the distance between the disk and bearing plate decreases in order to generate fluid pressure.

High Speed Machining — Cutting Tools and Machine Requirements

Abstract: A machine tool designed for high speed machining requires not only a high speed spindle but the capability of operating at rapid feed rates with high accuracy. Commercially available machine tools meeting this specification are reviewed and a list of machines presented, including costs. An alternative approach is to retrofit a high speed spindle to an existing machine using one or more of the spindle designs available. Such designs involve the use of angular contact ball bearings, magnetic bearings or air bearings; these are assessed. Tooling is also important and the paper refers to appropriate tool materials and geometry, aspects of tool interface quality and dynamic balancing. Finally, the traditional ISO taper is compared to the new HSK taper.

Analysis of mass transfer effects on the performance of journal bearings using micropolar lubricant

Abstract: In this paper the static and dynamic characteristics of a finite hydrodynamic journal bearing with micropolar lubricant are analyzed. The effects of mass transfer of solid additives and contaminants in the lubricant oil, on the bearing characteristics are considered in this study. A generalized form of Reynolds equation is derived from the fluid flow equations with the effects of mass transfer across the fluid film considered. The generalized Reynolds equation is solved using Galerkin's weighted-residual finite element method to obtain the fluid pressure distribution in the bearing. The various static and dynamic characteristics are subsequently obtained and presented.

Hydrostatic/hydrodynamic flywheel bearing for a press

Abstract: A hydrostatic/hydrodynamic flywheel for a press including a flywheel mounted for rotation about a non-rotating quill. A bronze bushing is disposed between the quill and flywheel. Hydrostatic pad areas are located on the quill opposite the bushing. These pad areas are flooded with pressurized oil or liquid to create a hydrostatic bearing area. During operation, flywheel and bearing rotation cause a hydrodynamic bearing effect to occur. The hydrostatic/hydrodynamic bearing eliminates the need for conventional anti-friction roller or ball bearings, provides indefinitely long life with full-film lubrication, high shock load capacity, high vibration damping, and a high value of radial and tipping stiffness.

Experimental temperature and pressure profiles for two steadily loaded journal bearings

Abstract: Experimental temperature and pressure profiles for a steel and a bronze bearing are examined. The comparisons show systematic differences between these otherwise identical bearings. These comparisons suggest that there would be merit in including thermal deformation in the analysis if high accuracy were required. The additional accuracy obtained could be especially important in accurately predicting the characteristics of sensitive high performance turbomachinery.

Severity Estimation of Cracked Shaft Vibrations within Fluid Film Bearings

Abstract: The equations of motion, with four degrees of freedom, taking into consideration the flexibility, damping and cross coupling of the fluid film bearings are derived for a cracked Jeffcott rotor supported on fluid film bearings. Dimensionless equations are developed for dynamic radial load, dynamic pressure developed in the fluid film bearings and coefficient of dissipation considering the journal vibrations in two harmonics; bearing fluid film stiffness and damping coefficients. These are applied to a cracked Jeffcott rotor supported on different types of bearings, i.e., cylindrical journal bearings, offset cylindrical bearings, tilting pad journal bearings and three-lobe bearings. Based on the allowable dynamic pressure developed in the fluid bearings, the severity of cracked shaft and allowable crack depths are estimated in this study. Measurement of dynamic pressure and dissipation for monitoring the crack growth is suggested. However, 2x vibration is the best indicator of cracks in the shafts. Presente...

Elasto-hydrodynamic lubrication of centrally pivoted thrust bearings

Abstract: Textbooks on lubrication show that a centrally pivoted hydrodynamic plane slider bearing can carry no load, and imply that in practical bearings the pivot must be offset. In practice offset pivots are the exception. This is attributed in the technical literature to a complex combination of thermal and elastic distortions. We show that operation is in principle possible purely as the result of the hydrodynamic pressures bending the pad to a desirable shape. Calculations for a wide pad suggest that successful operation requires only that a parameter p/4/(E/hmin) lie within the very wide range 20-330.

Model-Based Investigation of Friction During Start-Up of Hydrodynamic Journal Bearings

Abstract: An analysis is developed for the time-variable friction during the start-up of rotor system. The analysis is based on a dynamic friction model that has been developed from the theory of unsteady lubrication and can describe the observed friction characteristics. The model reduces to the Stribeck curve of friction versus steady velocity, and shows hysteresis curves in oscillating velocity. The Dahl effect of a presliding displacement before the breakaway is also included. The results indicate that the friction characteristics and energy friction losses, during the start-up, depend on a set of dimensionless parameters that represent the bearing as well as the dynamic system. The study shows that appropriate design and operation can prevent stick-slip friction and minimize wear during start-up.

Multimode pad-type hydrodynamic thrust bearings

Abstract: A hydrodynamic bearing that includes a carrier (10) and a plurality of bearing pads (1120, 1121) circumferentially-spaced about the carrier (10). The bearing has a multimode configuration for supporting a shaft that rotates in two or more distinct modes. The multimode bearing includes a carrier (10) for supporting two or more distinct sets of bearing pads (1120, 1121). Each set of bearing pads (1120, 1121) includes bearing pads (1120, 1121) that include a pad portion (1126, 1129) and a support portion (1124, 1125, 1130). The bearing pads (1120, 1121) of each set are supported by the carrier (10).

Accelerated Natural Convergence for Pivoted Slider Bearings

Abstract: A solution technique is discussed which accelerates the convergence of the pivoted slider bearing problem. The technique is based on a fully populated, three-degrees-of-freedom stiffness matrix for the hydrodynamic lubricating film. This matrix is developed using a unique perturbation method which, when used in conjunction with a finite element formulation of the Reynolds equation, yields the bearing stiffnesses in a computationally efficient manner. The resulting natural convergence of this hydrodynamic stiffness approach is examined for a typical rigid disk magnetic recording slider. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Lahaina, Hawaii, October 16–20, 1994

Fluid injector for gas- or hydrostatic-bearings having passive control

Abstract: An injector for a fluid bearing has a passive-control construction whose response is determined by the interaction of a spring spider (2, 3) whose centre (3) moves to regulate the control gap (5) with variable damping promoted by pressure differences.The fluid path during operation commences at the protective housing (9) in the chamber (7) from where it passes through the pierced apertures (8) in the spider (2, 3) to the ring channel (6), the control gap (5) and thence via the central bore (10) to the bearing gap (11).The dynamics of the system are such that a combined response to proportional, integral and differential components of change is obtained.