• Tribology and Lubricants
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• 제37권6호
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• pp.246-252
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• 2021

Among the engine components of an internal combustion engine, the valve train is a series of systems that supply intake gas to the combustion chamber and operate intake and exhaust valves that discharge exhaust gas. If excessive wear occurs in the valve train system, the suction and exhaust valves do not open and close on time, which leads to abnormal combustion and exhaust gas. In this study, we conduct experiments and analyses on friction and wear characteristics of the valve train system. Moreover, we experimentally study the correlation between the pinball and pinball cap on engine oil lubrication, friction experiment, wear amount analysis, and surface analysis. Specifically, we experiment using Ball on reciprocating tribo-tester and apply commercial engine oil sold on the market engine oil. We construct the experimental conditions for each new oil and oil. Accordingly, the completed specimen was subjected to a confocal microscope to check the wear volume, observe the surface of the specimen, and confirm the elemental components using a scanning microscope (SEM) and an energy dispersion X-ray spectrometer (EDS). Through this experiment, we analyze the friction and wear characteristics of valve train components according to engine oil grade, and the obtained data serve as an effective engine oil management method.

• Tribology and Lubricants
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• 제16권4호
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• pp.289-294
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• 2000

This paper present the contact stresses, which considers the shear stress at the cam and follower interface in the direct acting type valve train system of a high speed engine. To determine the contact condition, the normal contact forces are calculated by using the lumped mass dynamic modeling. The line contact is considered between the cam and follower interface. The variations of dynamic stresses are presented as a function of camshaft rotational angle. Also the effects of various design parameters are investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.269-270
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• 2006

• 한국세라믹학회지
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• 제35권2호
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• pp.172-179
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• 1998

Valve lifter namely tappet is supported by lifter hole which is located upper side of camshaft in cylinder block transforms rotatic mvement of camshaft into linear movement and helps to open and shut the en-gine valve as an engine parts. The face of valve lifter which is continuously contacting with camshaft brings about abnormal wears such as unfair wear and early wear because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears therefore The valve lifter cast in me-tal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance As a results the optimum process conditions like injection condition mixture ratio and debonding process could be established. After sintering fine-sinered dual microstructure in which prior ${\alpha}$-SiC matches well with new SiC(${\beta}$-SiC) produced by reaction among the ${\alpha}$-SiC carbon and silicon was obtained. Based on the study it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100-1200 bending strength (300-350 Pa) fracture toughness(1.5-1.7 Mpa$.$m1/2) Through engine dynamo test-ing SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such as early fracture unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resis-tance relaibility and lightability.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.39-48
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• 2014

Variable valve actuation system is one of the widely used techniques to improve the fuel efficiency and power of automotive engines. 2-step variable valve actuation systems are also paid attention for the application to direct acting type valve train systems. Besides its advantages in size, weight, relatively simple structure, ets, however, 2-step variable valve actuation system has inherent disadvantages in dynamic instability of switching system to alter discontinuous lift modes. In this study, both experimental and analytical studies are performed to understand the dynamic behavior of a switching mechanism of a 2-step variable valve actuation system, and present a design method to improve its dynamic instability.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.110-115
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• 1999

Experimental study is conducted to clarify the pneumatic characteristics of brake system for freight car. KNR(Korean National Railroad)'s freight cars have the laden-tare type control valve of brake system. But, laden-tare type control valve has some shortcomings to match the high speed freight car. Newly developed diaphragm type control valve is introduced to adopt freight car for speed-up. The test using the formated train set consisted of 21 cars is conducted to estimate the pneumatic braking efficiency of the mixed train set. From the results of experiment, the pressure characteristics of each brake cylinder show similar patterns qualitatively. But, in the case of release and brake application, quantitative pressure values of brake cylinder are different.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.151-159
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• 1998

디젤 엔진의 푸쉬로드 타입의 밸브 트레인에서의 힘의 전달 과정을 기구학적 응용을 통하여 구하였다. 이러한 힘의 최종 전달 단계인 캠과 평판 종동물의 접촉에서의 작용하중과 상대 운동 속도를 계산하였고 접촉면에서의 유막 두께를 고체면의 탄성변형을 고려하여 계산하였다. 특히 탄성 유체 윤활의 해석을 하는데 있어서 안정성과 수렴성이 우수한 멀티그리드 멀티레벨 기법을 사용하였으며 동하중 상태를 고려하여 유막 두께를 계산하고 기존의 정상상태의 해석해와 비교하였다.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.85-92
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• 2002

This paper presents the effects of design and operating parameters to meet the static and dynamic performances of the electro-mechanical valve(EMV) actuator which can provide more flexible controllability of valve events compared to conventional variable valve actuation devices. The model of the EMV system was also set up and applied to identify the dynamic behavior of the system. And the effects of external disturbances were also investigated such as cylinder pressure, armature neutral position and current supplying time effects and so on. Experiments were carried out to verify the model using the prototype actuator on test bench, it was found that there is a relatively good agreement between experimental data and modeling results. Also, the actuators meet the general engine speed range (over 6000rpm) and the variable valve event control for various VVT effects.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1929-1934
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• 2011

Recently the maximum speed becomes the most important performance in high speed train. But the speed up of train will not give the passenger good riding comfort. The semi-active suspension system by using variable damper with hydraulic solenoid valve is used to solve this problem. But the variable damper with hydraulic solenoid valve requires tank for supplying fluid. In this study, the MR(Magneto Rheological) damper was considered instead of hydraulic variable damper in order to improve riding comfort. Dynamic simulation was conducted for semi-active suspension system with MR damper was made by using Matlab-Simulink S/W. According to control strategy of MR damper for improving ride comfort in railway vehicle, The riding comfort of the railway vehicle with semi-active suspension system was analyzed and compared with conventional suspension system by using the program.

• Tribology and Lubricants
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• 제13권4호
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• pp.53-59
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• 1997

The camshaft locus at camshaft beating in a direct acting OHC valve train system has been investigated using the transient method. Forces applied to the camsfiaft are composed of two components, one is the transfer force between the cam and the tappet, the other is the frictional force. These forces have been calculated using the lumped mass model and the elastohydrodynamic lubrication theory. The alternating direction implicit method has been used for the numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for the transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As a result of the analysis, it has been found that camshaft bearings were mainly in the hydrodynamic lubrication condition.