• Tribology and Lubricants
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• 제14권1호
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• pp.23-27
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• 1998

The characteristics of friction in direct acting OHC vane train system have been investigated by the comparison of experimental and theoretical results. A modified friction model was presented to calculate the friction force at cam/tappet contact. A simple experimental system was evaluated to measure the friction force and the camshaft driving torque. The friction force was measured by using the dynamic loadcell. Good agreement was found between theoretical and experimental results in friction force, but there was a little difference in driving torque.

• 한국융합학회논문지
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• 제8권10호
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• pp.193-199
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• 2017

기계적 태핏은 유압 태핏과 비교하여 원가와 마찰 손실을 줄일 수 있어 사용된다. 그러나 기계적 태핏은 캠과 밸브 사이의 간극을 조절하는 기능이 없으므로 밸브의 열팽창을 고려하여 캠과 밸브 사이의 거리를 측정하여 선정된다. 그러므로 충분한 워밍 업 후에는 밸브 간극이 거의 없지만 그 전에는 밸브 간극이 존재한다. 특히 냉간 작동 조건에서는 비교적 큰 편이고 소음과 진동 같은 문제를 발생시킬 수 있다. 본 논문에서는 밸브 간극을 변경시켜 가며 각각의 조건에서의 밸브 리프트, 속도, 가속도, 시팅 속도, 바운싱 높이 등에 대하여 시험과 해석을 통하여 연구되었다. 밸브 간극이 증가할수록 램프 구간이 감소하게 되어 밸브의 거동에 좋지 않은 영향을 미치는 것을 확인할 수 있었다.

• 한국자동차공학회논문집
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• 제4권6호
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• pp.97-108
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• 1996

A modeling technique is proposed for dynamic simulations of OHC valve trains with HLA(hydraulic lash adiuster). HLA is expressed by an air-oil mixture model considering HLA leak-down and aeraton effects. A compact nonlinear equation is derived which describe the short term dynamic behavior of the HLA. Valve spring is analyzed by a distributed parameter model including nonlinear characteristics in the spring surge phenomena. Global behavior of the remaining valve train is expressed by a lumped mass model. The experiental results prove that the simulation model developed here is accurate and useful for the dynamic simulations of OHC valve trains with HLA.

• 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.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.185-192
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• 2002

This paper focused on the dynamic behavior of camshaft in a direct acting type valve train system. To investigate camshaft behavior, transient vibration analysis is performed by using the transfer matrix method. The camshaft is treated as lumped mass system supported by spring and damper. Front the presented analytical model, we could predict dynamic behavior of camshaft, shaft locus within bearing and bearing load. The presented mode and results will be very helpful to design the optimal camshaft and valve train system.

• Tribology and Lubricants
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• 제14권3호
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• pp.81-86
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• 1998

The purpose of this paper is to measure the rotational speed of tappet in OHC valve train system. Tappet has eccentricity about cam center, which induces the tappet rotation and prevents from wear. In this paper, the experimental test rig which composes of one cam system is developed to measure the tappet rotation by using the laser generating system, rotary encoder, optical fiber, and photo transistor. The direction of tappet rotation is judged from the oder of optical signal. As results of experiment, average and instant rotational speed and average rotation angle per one cam revolution are presented. Measured results show that eccentricity ratio is dominant factor for the tappet rotation, and tappet is rotated at the base circle.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.105-111
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• 2003

The valve train system of engines has long been a sensitive area with respect to wear performance because of the high contact loads and surface sliding speeds encountered. In particular, wear problems of load-carrying components in relative motion, such as cam and tappet in valve train system have made troubles. To overcome these problems, combination of proper materials is important, as well as selecting of high wear performance materials. This paper presents the experimental result of friction and wear properties of ca/tappet materials. To investigate friction and wear properties for several combinations of materials, using commonplace tribometer(Plint 77, reciprocating type), we make a selection of a optimum material combination.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.34-43
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• 2002

This paper focused on the dynamic behavior of camshaft in a direct acting type valve train system. To investigate camshaft behavior, transient vibration analysis is performed by using the transfer matrix method. The camshaft is treated as a lumped mass system supported by spring and damper, From the presented analytical model, we could predict dynamic behavior of camshaft, shaft locus within bearing and bearing load. The presented model and results will be very helpful to design the optimal camshaft and valve train system.

• 동력기계공학회지
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• 제21권4호
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• pp.70-76
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• 2017

This paper presents the development of a Gas Valve Train (GVT) control system which is the core equipment of LNG fueled vessels. Due to the increasing worldwide demand for echo friendly green ship products, domestic companies urgently require to develop a core equipments for the LNG fueled vessels to secure worldwide markets in marine engineering. A LNG fueled engine generally equips the GVT, a fuel supply system that steadily supplies clean high-pressure LNG to the engine. The GVT requires a safety operational control system that can prevent any gas leakage accident, and a system that monitors operation status in real time. Therefore, we introduces a development for GVT control and monitoring system design and the design was systematically performed by means of functional analysis and differentiation of foreign advanced products.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.397-405
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• 2000

Many computational researches have been performed about EHL film thickness in the contact between cam and follower. However, those computations do not explain the characteristics of dynamic film thickness which means squeeze film effect. Without the consideration of transient term in the Reynold's equation, the predicted film thickness has large difference from the actual film thickness. In this study, we have investigated the kinematic and dynamic simulations of rocker-arm valve train system. From the simulation, the applied load and the entraining velocity of the lubricant between cam and follower are obtained and with these values the dynamic film thickness is computed by Newton-Raphson method and compared with the steady state film thickness.