Pumping Characteristics of a Herringbone-Grooved Journal Bearing Functioning as a Viscous Vacuum Pump

1999 ◽  
Vol 122 (1) ◽  
pp. 131-136 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Ito ◽  
A. Takahashi
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Slip Flow ◽  
Laser Scanner ◽  
Vacuum Pump ◽  
Chamber Pressure ◽  
Design Parameters ◽  
Theoretical Predictions ◽  
Flow Effects ◽  
Good Agreement

A laser scanner motor with low power and high speed has been developed. This scanner motor uses a herringbone-grooved journal bearing which functions as a viscous vacuum pump. The windage power loss of a polygon mirror is reduced, since the air inside the pump housing is pumped out by herringbone-grooved viscous vacuum action. In this paper, the theoretical pumping characteristic of this bearing is investigated, using the narrow-groove theory and accounting for first-order slip flow. The effects of various design parameters on the pumping characteristics are discussed. Optimum geometric design parameters were found to obtain the minimum inner chamber pressure of the housing. The theoretical predictions considering slip flow effects are in good agreement with experimental measurements. [S0742-4787(00)01801-4]

A Method of Reducing Windage Power Loss in a Laser Scanner Mirror by Using the Pumping Effect of Herringbone-Grooved Gas Journal Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 506-509 ◽  
Author(s):  
S. Yoshimoto ◽  
A. Takahashi
Keyword(s):  
Power Consumption ◽  
Laser Beam ◽  
Power Loss ◽  
High Speed ◽  
Journal Bearing ◽  
Laser Scanner ◽  
Journal Bearings ◽  
Vacuum Pump ◽  
Low Power Consumption ◽  
Reduced Power Consumption

This paper proposes a newly developed laser scanner motor with low power consumption, operating at a high speed of rotation. The principle of the scanner motor is that of a herringbone-grooved journal bearing functioning as a viscous vacuum pump. The windage power loss of a polygon mirror can be reduced because the air inside the housing is pumped out by herringbone-grooved viscous vacuum pumps. The performance of the proposed laser scanner motor was measured under various conditions. It was subsequently found that the proposed scanner motor of a laser beam had much reduced power consumption and higher scanning accuracy than the conventional scanner motor in which the rotor is rotated in the air.

The Seal System in Aerostatic Journal Bearings for High Vacuum Chambers

2004 ◽  
Vol 126 (2) ◽  
pp. 310-315 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Yoshida ◽  
K. Yagi
Keyword(s):  
Pressure Distribution ◽  
Vacuum Chamber ◽  
Journal Bearing ◽  
High Vacuum ◽  
Journal Bearings ◽  
Vacuum Pump ◽  
Chamber Pressure ◽  
Design Parameters ◽  
Vacuum Chambers ◽  
High Vacuum Chamber

This paper investigates the performance of a seal system for an aerostatic journal bearing used in a high vacuum chamber. The seal system consists of axially spaced viscous seals and annular exhaust grooves that are located between the viscous seals. Each exhaust groove is coupled to a separate vacuum pump in order to achieve a vacuum chamber pressure of less than 10−3 Pa. The vacuum chamber pressure is affected by design parameters such as the number of viscous seal stages, seal length, seal gap, and exhaust tube conductance. The influence of these design parameters on the pressure distribution across seal regions and the vacuum chamber pressure are discussed theoretically. It is subsequently shown that an aerostatic journal bearing with three-stage seal system installed can obtain a reduction in the vacuum chamber pressure almost to the ultimate pressure of a vacuum pump, providing there is no leak or outgassing from materials.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

Stability of Water-Lubricated, Hydrostatic, Conical Bearings With Spiral Grooves for High-Speed Spindles

2001 ◽  
Vol 124 (2) ◽  
pp. 398-405 ◽  
Author(s):  
S. Yoshimoto ◽  
S. Oshima ◽  
S. Danbara ◽  
T. Shitara
Keyword(s):  
High Speed ◽  
Water Pressure ◽  
Rotating Shaft ◽  
Pressurized Water ◽  
High Speeds ◽  
Theoretical Predictions ◽  
The Stability ◽  
Stability Of Water ◽  
Spiral Grooves ◽  
Good Agreement

In this paper, the stability of water-lubricated, hydrostatic, conical bearings with spiral grooves for high-speed spindles is investigated theoretically and experimentally. In these bearing types, pressurized water is first fed to the inside of the rotating shaft and then introduced into spiral grooves through feeding holes located at one end of each spiral groove. Therefore, water pressure is increased due to the effect of the centrifugal force at the outlets of the feeding holes, which results from shaft rotation. In addition, water pressure is also increased by the viscous pumping effect of the spiral grooves. The stability of the proposed bearing is theoretically predicted using the perturbation method, and calculated results are compared with experimental results. It was consequently found that the proposed bearing is very stable at high speeds and theoretical predictions show good agreement with experimental data.

A Vacuum-Compatible Air Bearing: Design Analysis and Optimization

2007 ◽  
Vol 339 ◽  
pp. 37-44 ◽  
Author(s):  
G.H. Khim ◽  
Chun Hong Park ◽  
H.S. Lee ◽  
S.W. Kim
Keyword(s):  
Genetic Algorithm ◽  
Exhaust System ◽  
Optimization Method ◽  
Vacuum Pump ◽  
Chamber Pressure ◽  
Design Parameters ◽  
Air Bearing ◽  
Great Care ◽  
Spatial Design ◽  
Bearing Design

This paper describes the vacuum-compatible air bearing designed with a cascaded exhaust scheme to minimize the leakage of air in a vacuum environment. The design of the air bearing, including the differential exhaust system, required great care because several design parameters, such as the number of exhaust stages, diameter and length of the exhaust tube, pumping speed and ultimate pressure of the vacuum pump, and seal length and gap greatly influenced the leakage of air and thus the degree of vacuum. A leakage analysis was performed to estimate the chamber pressure and an optimization method based on the genetic algorithm was proposed under several constraint conditions. The results showed that the degree of vacuum improved dramatically compared to the initial design, and that the distribution of the spatial design parameters and technical limit of the pumping speed were well achieved.

scholarly journals Accumulator-free Hough Transform for Sequence Collinear Points

2021 ◽  
Vol 10 (2) ◽  
pp. 74-83
Author(s):  
Rudi Kurniawan ◽  
Zahrul Fuadi ◽  
Ramzi Adriman
Keyword(s):  
Computational Complexity ◽  
Hough Transform ◽  
High Speed ◽  
Laser Scanner ◽  
Measurement Data ◽  
Low Complexity ◽  
Autonomous Mobile Robots ◽  
Straight Line ◽  
Good Agreement ◽  
High Computational Complexity

The perception, localization, and navigation of its environment are essential for autonomous mobile robots and vehicles. For that reason, a 2D Laser rangefinder sensor is used popularly in mobile robot applications to measure the origin of the robot to its surrounding objects. The measurement data generated by the sensor is transmitted to the controller, where the data is processed by one or multiple suitable algorithms in several steps to extract the desired information. Universal Hough Transform (UHT) is one of the appropriate and popular algorithms to extract the primitive geometry such as straight line, which later will be used in the further step of data processing. However, the UHT has high computational complexity and requires the so-called accumulator array, which is less suitable for real-time applications where a high speed and low complexity computation is highly demanded. In this study, an Accumulator-free Hough Transform (AfHT) is proposed to reduce the computational complexity and eliminate the need for the accumulator array. The proposed algorithm is validated using the measurement data from a 2D laser scanner and compared to the standard Hough Transform. As a result, the extracted value of AfHT shows a good agreement with that of UHT but with a significant reduction in the complexity of the computation and the need for computer memory.

scholarly journals Part II—Case Studies for a Synchronous Thermal Instability Operating in Overhung Rotors

2004 ◽  
Vol 10 (6) ◽  
pp. 477-487 ◽  
Author(s):  
A. C. Balbahadur ◽  
R. G. Kirk
Keyword(s):  
Theoretical Model ◽  
Case Studies ◽  
Thermal Instability ◽  
Journal Bearing ◽  
Computer Programs ◽  
Tilting Pad ◽  
Theoretical Predictions ◽  
Overhung Rotors ◽  
Tilting Pad Journal Bearing ◽  
Good Agreement

In Part I, a theoretical model was developed for a synchronous thermal instability that is caused by differential viscous shearing in bearings of overhung rotors. This second part used computer programs, which were based on the theoretical model, to examine various case studies that pertain to this thermal instability. Both plain and tilting pad journal bearing rotors were examined and good agreement was found between the theoretical predictions and the practical results.

scholarly journals Theoretical Determination of Porpoising Instability of High-Speed Planing Boats

1978 ◽  
Vol 22 (01) ◽  
pp. 32-53 ◽  
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Theoretical Method ◽  
Theoretical Determination ◽  
Damping Characteristics ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Good Agreement

A theoretical method is derived for predicting trim angle and speed coefficient at the inception of propoising of prismatic planing hulls. Although equations are derived for the surge, pitch, and heave degrees of freedom, it is seen that the effect of surge is small at ordinary operating trim angles. Comparisons of theoretical predictions with existing experimental data on coupled pitch and heave porpoising show reasonably good agreement for a wide range of speed coefficients, load coefficients, and deadrise angles. The theory may also be used for estimating the natural frequencies and damping characteristics of prismatic hulls in the stable, high-speed planing range.

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