• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.466-470
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• 2000

Externally pressurized air journal bearing has been widely used in high-speed spindle system and precision machinery because of its characteristics such as substantially low frictional loss, low heat generation and averaging effect leading better running accuracy. But air journal bearing have a disadvantage of the low load capacity due to the low viscosity. In this paper, The air journal bearing design to overcome the defects of air bearing such as low stiffness and dimping coefficients was investigated theoretically.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.950-953
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• 2002

Trepan prevents wear of an inside part of a bearing when the initial shaft rotates. It continuously contacts with the eccentric part of the shaft in rotation and is loaded repeatedly. Therefore, even if an early crack of a trepan part is small, a crack progresses by a repeated load. If a crack progresses, very small chips come out. This is pill in the rotor and prevents rotation of the compressor. There can be leaks in a microgroove and extreme wear can occur due to lack of oil on the surface contact pan. Therefore, this study was carried out to compare and investigate trepan strength and deflection characteristics between trepan locations and dimension changes using a finite element method and search a motor bearing for a model with bigger stiffness of a trepan part and the same deflection. And then. five different types of the oil groove model were chosen to prevent small crack and considered also machining ability and the analysis was carried out on oil feeding flow.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.261-266
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• 2003

The present paper theoretically investigates characteristics of moment balance of a tilting-pad thrust bearing. Pressure of lubricant film of the bearing was computed using tile finite element method, and average film temperature was estimated from the heat balance over a pad. From the investigation, it has been found that different two sets of tilt angles satisfy moment equilibrium of the pad about tile pivot for a given pivot location. The tilt angles converged depend upon initial tilt angles assumed. Quite different bearing performance, including load capacity, film thickness, and temperature, is shown to be obtained based on choice of the initial tilt angles.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.273-280
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• 2003

The purpose of the paper is to investigate the noise characteristics of cylindrical roller bearings under radial load. The effects of radial clearance of the bearing, viscosity of the lubricant and number of the roller on the noise of the bearing are also examined. The results and discussions of the present paper might aid in the low-noise design of the cylindrical roller bearing.

• Journal of KSNVE
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• v.5 no.1
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.865-866
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• 2006

Bearingless Switched Reluctance Motor(SRM) have combined characteristics of SRM and magnetic bearing. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Bearingless SRM is simple structurally because the permanent magnet does not exist and bearing does not take the influence at the environment because it does not exist and has strong torque, and loss of bearing by bearing current has the advantage not to exist. In this paper, a design method of bearingless SRM for suspension power and starting torque is proposed. The design model is implement by maxwell.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1597-1606
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• 2003

Static analysis using hybrid finite element(FE) method has been applied to characterize the influence of position, runout and thickness errors of the sun, ring and planet on the bearing forces and critical tooth stress. Some guidelines for tolerance control to manage critical stress and bearing forces are deduced from the results. Carrier indexing error planet assembly and planet tooth thickness error are most critical to reduce planet bearing force and maximize load sharing as well as to reduce critical stresses. Sun and carrier bearing forces due to errors increase several times more than those of normal condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.80-87
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• 1998

In this study, the effects of residual shaft bow and flexible bearings of a single disk rotor are investigated. The stiffness coefficients of a shaft with initial deflection are different from those of a straight shaft. The stiffness coefficients are calculated using Castigliano theorem considering initial deflections. The stiffness coefficients, which are obtained in this study, are in good agreement with FEM results. The speed which causes zero amplitude is shown to be the square root of the ratio of residual bow amplitude to unbalance eccentricity in the case of rigid bearings and isotropic flexible bearings, but not in anisotropic bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.334-339
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• 2001

The nonlinear vibration characteristics of hydrodynamic journal bearings with a circumferentially groove are analyzed numerically when the external sinusoidal disturbances are given to the rotor-bearing system continuously. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis which uses the Reynolds condition. It is found that the difference between linear and nonlinear analysis is much more remarkable as the amplitude of external disturbance increases, and it depends upon the excitation frequency of external disturbance. It is also shown that the cavity region in the fluid film is increased as the amplitude or excitation frequency of external disturbance increases. The whirling center of the steady state orbit moves closer to the bearing center as the amplitude or the excitation frequency of the external disturbance increases because of smaller range of full film region.

• Tribology and Lubricants
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• v.13 no.2
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• pp.16-26
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• 1997

In this paper, the characteristics of lubrication and wear phenomena of journal bearing with respect to film parameter and Sommerfeld number variation are investigated experimentally and the design criterion for the hydrodynamic journal bearing is presented to avoid wear and seizure. Experimental work is performed with various rotating speed and load, and lubricant is used synthetic oil and mineral oil. By the results of the experiment, it is found that friction coefficient is decreased as Sommerfeld number is decreased, and that wear phenomenon is observed when Sommerfeld number is below $9$\times$10^{-4}$ and there are much alike in wear properties between synthetic and mineral oil.