• 오토저널
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• 제14권2호
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• pp.110-119
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• 1992

Crank pin temperatures were measured and analyzed to find out practical method which can predict the engine bearing reliability. The measuring points were determined to be near the MOFT region and far from that by theoretical calculation. The effect of engine running condition, oil temperature, the change of oil circuit into bearing and crankshaft endplay on crank pin temperature were experimentally tested. The result obtained was as following. The crank pin temperature was dependent on oil film thickness and directly influenced by the change of test condition. Also, the length of the crankshaft endplay was confirmed to be critical to connecting rod bearing failure. In conclusion, we found that the measurement method of crank pin temperature can be used for predicting the engine bearing reliability.

• 한국정밀공학회지
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• 제30권8호
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• pp.864-869
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• 2013

As the size of mechanical components decreases, capillary forces and surface tension become increasingly significant. A major problem in maintaining high reliability of these small components is that of large frictional forces due to capillary action and surface tension. Unlike the situation with macro-scale systems, liquid lubrication cannot be used to reduce friction of micro-scale components because of the excessive capillary and drag forces. In this work, the feasibility of using evaporation to coat a thin film of organic lubricant on a solid surface was investigated with the aim of reducing friction. Petroleum and silicone oils were used as lubricants to coat a silicon substrate. It was found that friction could be significantly reduced and, furthermore, that the effectiveness of this method was strongly dependent on the coating conditions.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.159-165
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• 1998

Bearing design of turbo type geared centrifugal air compressor for low vibration level has been studied. The Transfer Matrix Method was used in this paper to analyze the air-compressor consisting of impellers, multi-stage geared rotors, and oil-film hearings. We have to consider this air-compressor as multi-geared rotating system, because characteristics of rotor-bearing system are different from conventional characteristics of non-rotating system. From the view point of Rotordynamics, the stiffness and damping coefficient of oil-film bearing in case of compressor system are more sensitive than other design parameters such as shaft length, shaft diameter and the weight of impellers, etc. Therefore, the stiffness and damping coefficients on each bearing were considered as design parameters. As the result of this study, turbo type air compressor with low vibration level can be achieved.

• Journal of Mechanical Science and Technology
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• 제15권6호
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• pp.685-692
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• 2001

This paper reports on the mixed lubrication characteristics between the cam and the tappet contact surface of direct acting type valve train systems. First, the dynamic characteristics are solved by using the lumped mass method to determine the load conditions at the contact point. Then, the minimum oil film thickness is calculated with consideration of elastohydrodynamic line contact theory and the friction force is obtained by using the mixed lubrication model which separates the hydrodynamic and the boundary friction. Finally, the average surface temperatures are calculated by using the flash temperature theory. The results show that, there are some peaks in the friction force due to the asperity contact friction, and flash temperature at the position of minimum oil film thickness. It is thought that there is a relationship between the surface temperature and cam surface wear, and therefore, the analysis on the worn cam profile has been performed.

• Tribology and Lubricants
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• 제15권1호
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• pp.68-76
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• 1999

This paper presents the nonlinear characteristics of the oil lubricated hydrodynamic journal bearing. 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 journal bearing when an external sinusoidal shock is given to the system. The oil film force is obtained by solving the finite width Reynolds equation at each time step by the solution of the column method. Frequency response function and journal orbit obtained from both linear and nonlinear bearing simulations are compared with each other.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.180-184
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• 2000

The dymanic properties of the high-Tc superconductor journal bearings used in the KEPRI flywheel energy storage system was experimentally estimated by using the imbalance excitation method. The test reveals that the superconductor bearings have very low stiffness compared to that of typical oil film bearings with similar geometry and almost the same amount of damping as in roller bearings, which may not be helpful for the system to pass through the critical speeds. However, it was found out that the cross-coupled stiffness and damping terms were almost negligible so that the system could be more stable than the one using lil film bearings. Also with proper design of the rotor-bearing system and accurate balancing of the rotor, the high-Tc superconductor bearing is one of the most viable alternatives to the conventional ones due to its oil-free, non-contact running capability in a vacuum environment, which is literally essential for highly efficient flywheel energy storage systems.

• Tribology and Lubricants
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• 제10권1호
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• pp.69-77
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• 1994

Oil flow pass of hermetic scroll compressor with back pressure chamber was described. Dynamic analysis was preceded in order to obtain the loads on the lubricating contacts. The mobility method of dynamically loaded journal bearings was applied to the crank jornal bearing and lower main bearing, and they could be designed to operate under fluid film lubrication. From the consideration of their film thicknesses and oil flow rates, optimal bearing clearances or other bearing dimensions could be assessed. The major friction loss was calculated to be from the axial force between the two scrolls. Therefore, it was suggested that the designers should be careful to reduce the over-turning moment on the orbiting scroll.

• Journal of Magnetics
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• 제22권2호
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• pp.291-298
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• 2017

In this paper, the distribution of internal magnetic induction intensity of oil-film bearing twined solenoids was proposed. The magnetic field was generated by solenoids and magnetized bearing. The magnetized bearing was simplified as solenoid model. The mathematical model of magnetic induction intensity at any point of finite solenoid was deduced. Through experiment method, the distribution of the internal magnetic induction intensity of oil-film bearing and the magnetizing current formula of bearing was obtained. Further, the magnetic induction intensity distribution of magnetization bearing was solved successfully. The results showed that the magnetic induction was a second-degree parabola with open upwards along the axial plane and the distribution of magnetic induction intensity was opposite to the rule of magnetic induction intensity generated by solenoids. In addition, the magnetic flux density increased linearly with the increase of current.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.82-87
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• 1997

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric parts and gas forces induced by the pressure difference between compression and suction gases. Rotor-journal bearing system is nonlinear since the stiffness and damping coefficients of the lubricating oil film are not constant in the bearings. The system is considered as a coupled problem of flexible rotor and the journal bearings. Bearing reaction force is calculated from pressure of oil film using Reynolds equations in journal bearings. Pressure distribution in journal bearing is analyzed by finite difference method. The dynamic response of rotor and bearing characteristic are discussed when rotary compressor has a relative misalignment.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.241-245
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• 1998

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 journal bearing when an external sinusoidal shock is given to the system. The oil film force is obtained by solving the finite width Reynolds equation at each time step by the solution of the column method. Frequency response functions obtained from both linear and nonlinear bearing simulations are compared with each other.