Showing papers on "Fluid bearing published in 1992"

Effect of the hydrodynamic bearing on rotor/stator contact in a ring-type ultrasonic motor

Abstract: A hybrid numerical analysis that includes the hydrodynamic bearing effect and elastic contact in a ring-type ultrasonic motor is presented. The two-dimensional time-dependent compressible Reynolds equation is solved numerically by a second-order time accurate, noniterative, factored implicit finite-difference algorithm. The rotor deformation is described by a one-dimensional Green's function. The contact problem is solved by an iteration method so that the contact condition and the hydrodynamic bearing condition are satisfied simultaneously. The results show that the hydrodynamic bearing effect, especially the squeeze effect, is significant for ultrasonic frequency contact of the rotor and stator. Surface roughness, contact area, and normal vibrating speed of the stator are important parameters in the hydrodynamic bearing. A disagreement between the friction coefficient needed in the numerical analysis and the experimentally measured one in a previous study. >

Nonlinear transient and frequency response analysis of a hydrodynamic journal bearing

Abstract: The traditional approach is to characterize the behavior and performance of fluid film hydrodynamic journal bearings by means of linearized bearing analysis. The objective of this paper is to examine the nonlinear characteristics of the said journal bearing. Results based on bearing stiffness characteristics, steady and transient vibration orbits, and frequency response functions obtained from both linear and nonlinear bearing simulations are compared with each other. Conclusions are drawn from the results obtained from a prototypical bearing configuration used as an example in this analysis

An analysis of gas-lubricated foil-journal bearings

Abstract: The foil journal bearing is essentially a series of thin overlapping circular metal foils, one end of which is cantilevered to the bearing and the other end rests on an adjacent foil. Typically, the radial load at the high temperature end (turbine) of a gas turbine engine is supported by a roller bearing. The high temperatures encountered at the turbine end result in reduced roller bearing life and also necessitate elaborate cooling and lubricating systems to keep the bearing temperatures within reasonable limits. Foil-journal bearings are simple, lightweight and well suited for such high temperature applications, and since they are self-acting air bearings the need for a lubricant supply system is obviated. The hydrodynamic pressure force in the air film generated by the journal rotation deflects the compliant foil surface resulting in a change in film thickness, and hence the pressure solution to the problem is of the elasto-hydro-dynamic (EHD) type. The nonlinear compressible finite-length Reynolds equ...

The Performance of Hybrid Journal Bearings in the Superlaminar Flow Regimes

Abstract: Previous work conducted on hybrid journal bearings has shown that a combination of hydrostatic and hydrodynamic lubrication principles leads to good load support over a wide range of speeds, including zero speed. Above the transition speed, particularly with large bearing diameters or low-viscosity lubricants, the mode of flow within the fluid film degenerates from that of pure laminar flow, through a transitional or vortex flow regime, to fully developed turbulent flow. This work presents a theoretical investigation of slot entry hybrid journal bearings operating in the superlaminar flow regimes. In particular, the work considers the effects of superlaminar flow on the optimization of slot entry hybrid journal bearings.

Fluid thrust bearing centrifugal disk finisher

Abstract: A centrifugal disk finisher includes a porous layer at the bottom of the vertical wall of the containment vessel. A pressurized fluid, preferably air, is forced through the porous layer so as to form a fluid bearing between the bottom of the porous layer and the spinning disk enclosed within the containment vessel. The containment vessel is levitated above the spinning disk by a small amount due to the presence of the fluid bearing, so that the disk spins without any contact with the containment vessel, thus reducing wear. The fluid bearing also acts as a seal, which repels particles from the interface between the disk and the porous layer due to the small height of the fluid bearing and its imperviousness to all but the most energetic particles.

Nonlinear spring supported hydrodynamic bearing

Abstract: A compliant hydrodynamic gas bearing comprises a nonlinear spring arrangement for supporting a plurality of tilting arcuate pads which hydrodynamically carry radial journal loads. The nonlinear spring support arrangement enables the bearing to provide increasing load-deflection capacity under extreme loads to limit deflection to a predetermined clearance. The spring arrangement provides nonlinear load-deflection capabilities while operating with a designed constant bending stress.

On the Mixture Flow Problem in Lubrication of Hydrodynamic Bearings: Small Solid Volume Fraction

Abstract: The lubrication problem of infinitely long slider bearings with a mixture of fluid and particulate solid at small volume fraction level is studied. Closed-form analytical solutions for pressure and shear stress are obtained for a class of solid aggregates. The results reduce to those of pure fluid in the limiting case. A parametric study of the bearing performance with particulate solid is presented.

Magnetic fluid bearing device

Abstract: PURPOSE: To simplify a seal structure of magnetic fluid and further to reduce deflection and wearing damage of a shaft part by holding the magnetic fluid in a clearance between a bearing part and a shaft part peripheral surface opposed to this bearing part and in the external space continued to this clearance. CONSTITUTION: In bearing parts 2, 3, a bearing surface is constituted of a circular annular bearing surface member 5 consisting of nonmagnetic material secured to the internal peripheral surface of a circular annular magnet or a circular annular bearing surface member 5 consisting of permeable material secured to respectively the internal peripheral surface in the vicinity of both poles. Accordingly, intense magnetic flux passes through the total surface of a bearing surface clearance S 4 between a shaft part 7 consisting of permeable material and the bearing parts 2, 3 consisting of magnets, to hold magnetic fluid 8 between the bearing parts 2, 3 and the shaft part 7. Further, a magnetic field is formed toward the shaft part also from a side surface of the bearing part, to hold the magnetic fluid 8 also in the external space continuous to the bearing surface clearance S 4 between a bearing surface of the bearing part and the shaft part 7 related to this bearing surface. COPYRIGHT: (C)1994,JPO&Japio

Device for manufacturing lubricant supply grooves in fluid bearings

Abstract: A system for manufacturing lubricant supply grooves in a fluid bearing, in which a worn working body can be replaced. A through-hole is formed in the tool body so as to receive the working body, and a working portion is formed having a predetermined curvature at both ends of the working body. Both ends of the working body protrude to the same height from the outer circumferential surface of the tool body.

Thermal and Non-Newtonian Effects on the Steady State and Dynamic Characteristics of Hydrodynamic Journal Bearings—Theory and Experiments

Abstract: Theoretical investigations are carried out for a plain journal bearing considering the influence of thermal effects on non-Newtonian lubrication. With reasonable assumptions, the steady state and dynamic characteristics are presented using a thermohydrodynamic analysis of a bearing lubricated by a nonlinear, i.e., cubic, fluid model. Experiments are conducted on a rig to study the steady state and dynamic performance of a full journal bearing with different types of non-Newtonian lubricants. Experiments include the measurements of eccentricity ratio, critical speed, and stability limit. The theoretical investigation reveals that the interaction of the non-Newtonian effect and the thermohydrodynamic effect is strong for friction, and the interaction effect is negligible in the case of eccentricity ratio, attitude angle, and lubricant flow rate. Further, for relatively high values of non-Newtonian parameter, αn , the effect due to the non-Newtonian parameter is not negligible. Presented at the 46th Annual M...

Dynamic pressure fluid bearing

Abstract: PURPOSE:To make a fluid bearing compact and its long-term use possible, and to improve its reliability by providing a bearing with an oil flowing route which accumulates oil functioning as working fluid and communicates with the atmosphere and at least one end of a spiral groove, and providing the end of the spiral groove with an oil supply passage under atmospheric pressure using the oil flowing route. CONSTITUTION:The one end of a oil flowing route 16 communicates with the atmosphere through a gap 17 between the outer periphery communicating with the atmosphere of rotary shaft 4 and a bearing 1 and a communicating hole 18 positioned near the end 9 of the spiral groove 3a. The other end of the oil flowing route 16 communicates directly with oil reservoirs 5, 6 through communicating holes 19, 20. In addition to that, the partial section of the oil flowing route 16 and groove end parts 11, 24, 25 are filled with oil 21 functioning as working fluid. The atmospheric pressure always acts on the ends 11, 24, 25 of spiral grooves 2a, 2b, 3b through the oil in the communicating holes 19, 20 and the oil flowing route 16, the communicating hole 18 and the gap 17. When the oil leaks from the end 9 on the opening side of the spiral groove 3a, the oil 21 in the oil reservoir 6 is supplied for a deficiency in the above oil from the end 25 of the spiral groove 3b.

Static pressure fluid bearing and positioning control device thereof

Abstract: PURPOSE: To provide a static pressure air bearing which prevents change of a bearing gap due to fluctuation of assembling precision or mechanical precision of the bearing or positional change caused by movement of the bearing. CONSTITUTION: A bearing comprises static pressure pads 5a, 5b for jetting fluid to an opposite surface to keep a gap between those and the opposite surface by static pressure, bias magnets 12a, 12b which work in the directions to reduce the gap, and coils 13a, 13b for modulating magnetic fields of the bias magnets. COPYRIGHT: (C)1993,JPO&Japio

Inertia Effect of the Fluid Particles on the Lubricant Flow in a Dynamic Thrust Bearings

Abstract: Closed form equations are derived from the fundamental principles for the evaluation of volume flow rate of lubricant in between the pads of a thrust bearing accounting for the centrifugal inertia effect. Two types of configuration i.e. parallel disk and nonparallel disk configurations are considered. The theoretical analysis is presented.

Improvements in bearings

Abstract: A machine is disclosed having novel air bearings for supporting one machine part for translational movement on another part in a first direction X. Each bearing takes the form of a track (5A,14,16) on one of the parts providing concave part-cylindrical bearing surfaces (5A,14A,16A) and pads 25 on the other part providing confronting convex part-cylindrical bearing surfaces 25A. The arc lengths of the part-cylindrical bearing surfaces are such as to provide restraint against relative movements between the machine parts in at least one sense of both of the two directions (Y,Z) orthogonal to the direction (X) of the translational movement. The advantages are relative cheapness of manufacture compared to vee- bearings and a capability of the bearings to self-align under load.

Magnetic fluid bearing device and rotary device

Abstract: PURPOSE:To improve a pressure resisting property of a seal at the pressure rise in a bearing section by disposing a magnetic fluid seal provided with an end ring and a bearing spaced therefrom in a magnetic pole piece and providing a dynamic pressure generating element in the magnetic fluid seal section. CONSTITUTION:A bearing device 2 consists of an inner race 10, permeable thrust collar 11 and non-magnetic outer race 12, and magnetic fluid 15 is supplied to a gap 14 between the inner and outer races 10, 12. A magnetic fluid seal is composed of magnetic pole pieces 20, 21, permanent magnet 17, non- magnetic ring 18 provided with a dynamic pressure generating groove 19, thrust collar 11 and magnetic fluid 15. The magnetic fluid 15 is strongly magnetized at the inside diameter end portions of the magnetic pole pieces 20, 21 in non- rotation of the bearing device to seal the magnetic fluid 15. When the internal pressure in the bearing 2 is increased by exothermic action in the rotation of the bearing, a fluid force is generated in the dynamic pressure generating groove 19 and the magnetic fluid 15 is shifted in the direction arrow to prevent the magnetic fluid from leakage in the distal end of the magnetic pole piece 20.

Dynamic pressure fluid bearing

Abstract: PURPOSE:To restrain generation of abraded powder and elongate the life of a bearing by forming a lubricating film made of a porous aluminium oxide film impregnated with lubricant on a bearing surface having a dynamic pressure generating groove in a dynamic pressure fluid bearing and making the bottom surface of the dynamic pressure generating groove of aluminum or aluminum alloy. CONSTITUTION:The surface of a shaft 1 is covered with a lubricating film 4 of a porous aluminum oxide impregnated with lubricant on portions except for a groove 3 for generating dynamic pressure. Aluminum or aluminum alloy itself is left exposed on the bottom surface 3a of the dynamic pressure generating groove 3. A dynamic pressure fluid bearing is light since a shaft 1 formed with the dynamic pressure generating groove 3 is made of aluminum or aluminum alloy, so that a radial load and thrust load acting on the bearing are small. As a result, the wear of a dynamic pressure radial fluid bearing R and dynamic pressure thrust fluid bearing S is few to improve durability.

Michelson interferometer with two rotating retroreflectors

Abstract: The stop-and-go operation is replaced by a continuous rotation. Thus the motion of the retros is much easier to handle:instead of sophisticated air bearings or linear slidings ball bearings are used. As the rotational axle is stressed by a biastension in axial direction no spurious lateral motion with reference to the optical axis is possible. Thus mechanicaldisturbances in lateral direction cannot effect the measurement.

Bearing device for magnetic disk

Abstract: PROBLEM TO BE SOLVED: To prevent a lubricant of dynamic pressure fluid bearings from splashing and sticking to the magnetic disk by shutting ventilation from a lubricating oil reservoir to the outside. SOLUTION: When a coil of a stator 34 of a driving motor is electrified, rotary force is produced on a rotor 33. Consequently, the hub 25 is rotated integrally with a magnetic disk D. At this point, the hub 25 is supported in the radial direction with its sleeve part 26 keeping in noncontact with a shaft 22. Now, since no vent holes are provided on both the dynamic pressure radial fluid bearing R and the dynamic pressure thrust fluid bearing S, it is impossible that the lubricant in the bearings is splashed out of such vent holes in rotating the hub 25. Moreover, all spaces between the hub 25 and a thrust plate 29 and also the shaft 22 can be filled with the lubricant without leaving air in assemblage. Therefore, the lubricant is never leaked outside the bearings on account of expansion of air due to a temp. rise.

Dynamic pressure fluid bearing turning device

Abstract: PURPOSE:To reduce friction between a rotary shaft and a thrust plate and prolong the life of a dynamic pressure fluid bearing by retaining the rotary shaft with a retaining rod, maintaining the layer of lubricating fluid between the rotary shaft and the thrust plate at the time of stopping rotation, and evacuating the retaining rod at the time of startup CONSTITUTION:A shallow groove 18 is engraved on the surface of a thrust plate 16 to form a dynamic pressure thrust bearing Also, a shallow groove 12 in the form of herringbone is engraved on the outer circumferential surface of a rotary shaft 1 to form a dynamic pres sure radial bearing A rod-shaped piezoelectric element 17 is mounted to a statioaary plate 19, and the stationary plate 19 passes through the hole part 16a of the thrust plate 16 to support the lower end of the rotary shaft 1 When this device is irrotational, the piezoelectric element 17 raises the rotary shaft 1 as voltage is not applied to the piezoelectric element 17, maintaining the thickness of the layer of lubricating fluid at the height of (a) At the time of startup, voltage is applied to the piezoelectric element 17 to evacuate it into the thrust plate 16 enabling this device to smoothly start rotation in the state that sufficient lubricating fluid interposes between them Then, the voltage of the piezoelectric element 17 is released when rotation is stabilized and the rise of the shaft is stabilized, returning the position of the piezoelectric element to the original length (a) and making the rising amount of the rotary shaft 1 to the height of (L)

Compound type fluid bearing device

Abstract: PURPOSE:To provide a compound type fluid bearing device which is used in a video tape recorder or the like and has a thrust bearing excellent in abrasion resistance and excellent rotational performance by low frictional torque CONSTITUTION:A dynamic pressure fluid bearing is used as a radial bearing 8, while a thrust bearing 7 is composed of a shaft 2 having a contact point on its end formed eccentrically from a shaft center by 15 to 100 micronmeters, and a thrust pad 3 abutting therewith A compound type fluid bearing device is thus realized with highly accurate rotational ability of the radial bearing and sufficient abrasion resistance of the thrust pivot bearing

High-output turbo-pump for liquid-fuelled rocket motor - has large-diameter rotary shaft with high pressure turbine and supporting and fluid bearings

Abstract: The turbo-pump consists of a large-diameter rotary shaft (22) carrying a high-pressure turbine (5) which forms a single pump stage to receive the liquid fuel through a suction duct (3) and deliver it under pressure through a feed duct (4). It has one bearing (23) to support the shaft (22) in a zone of reduced section situated in front of the turbine (5).There is a fluid bearing (24), able to withstand a high speed of rotation, situated in a zone of large section to the rear of the turbine, and at least one turbine stage (32, 33) to the rear of the fluid bearing. A high-pressure inductance fan (31) is situated in front of the bearing (23), and the turbo-pump is equipped with cast metal housing sections (1, 2, 38) of simple shape. ADVANTAGE - Simple and compact design, with reduced manufacturing costs.

Compound fluid bearing device

Abstract: PURPOSE:To provide a compound bearing device excellent in the wear resistance of a thrust bearing and rotating performance and having low frictional torque. CONSTITUTION:A dynamic pressure type fluid bearing is used for a radial bearing 8. A thrust bearing 7 is provided with a nearly spherical shaft end 2A and with a thrust receiver 4 tilted by 2/1000-12/1000 relative to a plane normal to a shaft 2. This provides a compound fluid bearing device having sufficient wear resistance of the thrust bearing 7 while maintaining high accuracy rotating performance of the radial bearing 8.

Fluid bearing device

Abstract: PURPOSE:To prevent mixing of thrust-oil with radial-oil in a fluid bearing device in a magnetic head cylinder, etc, by providing an oil-mixing preventing part utilizing centrifugal force generated at the time of rotation of the bearing part, between the thrust bearing part and the radial bearing part CONSTITUTION:When an upper cylinder 22 is rotated in a magnetic head cylinder, a dynamic pressure is generated in the radial bearing part 24 of a disc 23 so as to rotate a shaft 25 in non-contact manner On account of the direction of thrust, at this time, the upper cylinder 22 is rotated by grooves provided near a thrust bearing plate 27 with a thrust bearing plate 27 floated from the end face of the shaft 25 Thus, thrust-oil 37 is moved back in the direction of thrust by the effect of centrifugal force generated at the time when the tapered part 29 of the disc 23 is rotated, and with regard to radial-oil 38, a force positively accumulating this oil in an oil-mixing preventing part 28 formed into a recessed part is exerted on the oil by the effect of centrifugal force generated at the time of rotation of the tapered parts 29, 30, thus the radial-oil is not moved in the direction of thrust, and thereby mixing of the thrust-oil 37 with the radial-oil 38 can be prevented

Fluid bearing unit

Abstract: PURPOSE:To obtain a fluid bearing unit having excellent abrasion resistance and protected against damage due to brittleness by providing a bearing composed of ceramic material split in circumferential direction, a bearing housing resiliently supporting a bearing base, and an agitating board. CONSTITUTION:A rotary shaft 3 is coated with a super hard allay 4 and a bearing 5 composed of split ceramic material is arranged thereabout. Fluid to be fed from the bearing 5 is subjected to viscous centrifugal function by an agitating board 7 and thereby foreign matters contained in the fluid are introduced to a resilient body 6 supporting a bearing base without entering therein and then the foreign matters pass through the gaps of the resilient body 6 without breaking the water film. Furthermore, since the bearing base is resiliently supported by the resilient body 6, instantaneous impact load caused by an external force is absorbed through deformation of the resilient body 6. According to the constitution, quench crack or brittle breakdown due to impact can be prevented even if a ceramic material having low impact resistance is employed.

Fluid bearing type rotational head cylinder

Abstract: PURPOSE:To provide a fluid bearing type rotational head cylinder used in a video tape recorder or the like, which has a thrust bearing excellent in abrasion- resistance, and a bearing excellent in rotational ability with a low frictional torque. CONSTITUTION:A dynamic pressure fluid bearing is used as a radial bearing 8. A thrust bearing 7 has a shaft 2 whose one end is substantially semi- spherically formed. A thrust pad 4 is abutted against a contact point of the end of the shaft, eccentrically from a shaft center by 15 to 100 micrometers. A fluid bearing rotational head cylinder wherein high accuracy of rotational ability of the radial bearing is maintained and the thrust pivot bearing is provided with sufficient abrasion-resistance is obtained.

A Study of Transient Response of Flexible Rotors in High Speed Turbomachinery

Abstract: In many applications the design operating range of the turbomachinery may be well above the rotor first critical speed which leads to the problem of insuring that the turbomachinery performs with a stable, low-level amplitude of vibration.Under certain conditions of high speed and loading the rotor system can start orbiting in its bearing at a rate which is less than the rotor angular speed, and this phenomena is commonly known as whirling or whipping action. This whipping action may produce additional undesirable dynamic loads on the overall flexible assembly and eventually destroy the rotor. Some of this action is also transient in nature.Whirling is a self-exited vibration caused mainly by the fluid bearings and by the internal friction damping of the rotor. To understand this occurrence, a general dynamic mathematical model was derived considering also the complete viscous characteristic of hydrodynamic journal bearings.The general equations of motions of the system are obtained from Lagrange’s equation of motion. The system kinetic, potential, and dissipation functions are determined based on the generalized coordinates of the system.The journal displacements are related to the overall dynamics of the rotor using deformable bearings. The loads acting at the journals of the shaft are integrated from the fluid film pressure distribution in the journal bearings using mobility method.A unique mathematical model is formulated and solved. This model includes the elastic and inertial properties of the flexible rotor, the elastic, damping and inertial properties of supports and the hydrodynamic characteristics of the journal bearings.The equations of motions result in a system of nonlinear second order differential equations which are solved by using finite difference method. The solution of the equations of motions is used to plot maps of motion of journal centers.A computer program was implemented to aid in the solution of the system of equations and to verify analytical model. The computer program used test data available in literature and the results were compared to be very good.The analytical model and results obtained in this study can be of great help to designers of high speed turbomachinery.Copyright © 1992 by ASME