• 한국자동차공학회논문집
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• 제14권4호
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• pp.139-148
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• 2006

Valve train is one of the important noise sources in idling engines. Valve train noise comes mostly from two different impacts. One is the impact between cam and tappet at the beginning of the valve open period, which is an important source of impulsive noise of valve trains. The other is the impact between valve and valve seat at the closing of the valve open period. In case of mechanical lash adjusters, it is very difficult to control the initial impact. In this paper, we designed various types of cam profiles, especially in the opening ramp design, and investigated the effect of cam profiles on the magnitude of the initial impact. The effects that some cam design parameters have on the impulsive noise are also observed.

• 한국자동차공학회논문집
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• 제6권3호
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• pp.78-87
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• 1998

A dynamic model of direct-acting OHC valve train system has been used to determine the load conditions in the system. The modified equations for calculating the friction forces between cam and HLA, and at a camshaft bearing have been defined considering the lubrication conditions. Then, to understand the frictional characteristics in the system, a parameter study has been performed. As the results of the analysis, valve spring stiffness and preload have great effects on the friction in the system, but the effects of other parameters are negligible. So, how to design the valve train system with respect to the reduction of friction is to minimize the valve spring stiffness and preload in the limit of satisfying the dynamic constraints.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1364-1369
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• 2002

This paper introduces the development of the analysis and design program of valve train system. In order to verify the stability of design and improve the performance of system efficiently, it is required that integrated and interactive simulation program. The presented program is developed in the base of the object-oriented, capsulation, modulization, OLE (objected linking and embedding) and various design theory. It contains the expandability and flexibility of the structure. In addition to that, it is programmed to make the convenient user interface by using the visualization programming. This program can support the modification of the valve element as well as the development of the valve train system in the beginning of design. It is expected to save the cost and time for the design of valve train system.

• 한국자동차공학회논문집
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• 제17권4호
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• pp.63-71
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• 2009

The elastic effects of the valve train components are analyzed by using the finite element models of the rocker arm and valve. The whole equations of motion of the valvetrain of an internal combustion engine formulated by finite element techniques are solved by imposing the contact conditions with the augmented Lagrange multiplier method. The velocity and acceleration constraints as well as the displacement constraints are imposed on the contact points. The numerical simulations show that, even if the magnitude of the elastic deformation of the components is very small, it may have large effects on the valvetrain dynamics of a high-speed engine.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.286-291
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• 1998

The aim of this paper is to measure the tappet rotation in OHC valve train system. Tappet is eccentric from the cam center to rotate for preventing the partial wear. The experimental system is developed to measure the tappet rotation by using the laser beam and optical fiber. The characteristics of tappet rotation is presented for various operating conctitions. Specially, it is observed that tappet is rotated at the base circle.

• 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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• 제14권2호
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• pp.184-193
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• 2006

Rotation of intake and exhaust valves are very closely related to the long term durability of automotive engines. If the valves do not rotate even at a rated engine speed, it causes the uneven wear of the valve seat and valve head contact area, which eventually shortens the engine life. A principle of valve rotation mechanism was presumed based on some findings from experiments, and computer programs were developed to simulate the valve rotation phenomena. In this study we investigated the valve rotation mechanism by using the computer simulation models.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.505-506
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• 2007

• 한국자동차공학회논문집
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• 제19권1호
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• pp.125-132
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• 2011

The dynamic characteristics of valve train are responsible for the dynamic performances of engine. We derived the equation of motion for 6 degrees of freedom model of the valve train. Computer model is also developed with flexible multibody model considering contact between components. The simulation results with these two models are compared with experimental results. We investigated the effect of the two spring models, TSDA (Translational Spring Damper Actuator) element and flexible body model, on the valve behavior and spring force. It is found that the dynamic behavior of the two models are not very different at normal operational velocity of the engine. By modeling contact between cam and tappet, the stress distributions of the cam were found. Using stress distribution obtained, contact width and contact stresses of the cam surface were calculated with Hertz contact theory.