• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.283-290
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• 2000

To maintain the specific volumetric efficiency of a heavy-duty diesel engine, an understanding of the behavior of each part of the valve train system is very important. The stiffness of the valve train system has a strong influence on the behavior of the valve train than valve clearance, heatresistance, or the durability of parts. In this study, a geometrical cam design profile using a finite element model of the valve train system is suggested. The results of the valve behavior according to the change in stiffness is analyzed for further tuning of the valve train system.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.184-192
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• 2001

Cam/tappet wear is one of the critical concerns in valve train deign. Maximum contact stress and minimum oil film thickness between the cam and tappet are usually checked for the estimation of wear characteristics. If the two extreme cases arise simultaneously, there is a strong possibility of cam/tappet wear. In this paper, effects of valve train layout on the wear characteristics were studied. Especially for swinging arm type valve trains, initial geometric layout must be very carefully defined to avoid wear problems. The study was performed fur an end pivot type OHC valve train, which had severe wear problems. Analysis results show that some geometric parameter affect very sensitively on the wear characteristics. Experiments were also performed for the original and modified valve trains, which strongly support the analysis results.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.30-37
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• 1998

It is well known that reduction of friction loss due to the valve train system greatly affects on improvement of fuel economy in internal combustion engine. In order to investigate friction characteristics of valve train system we carried out friction force measurement using test rig developed by ourselves. From test results, we concluded that characteristics of lubrication and friction torque on the valve train system such as mixed and hydrodynamic was mainly governed the contact type between cam and tappet.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.110-122
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• 1996

The objective of this study is to understand the dynamic characterictics of OHV type valve trains and to design and optimal cam profile which will improve engine performance. A numerical model for valve train dynamics is presented, which aims at both accuracy and computational efficiency. The lumped mass model and distributed parameter model were used to describe the valve train dynamics. Nonlinear characterictics in the valve spring behavior were included in the model. Comprehensive experiments were carried out concerning the valve train dynamics, and the model was tuned based on the test results. The dynamic model was used in designing an optimal cam profile. Because the objective function has many local minima, a conventional local optimizer cannot be used to find an optimal solution. A modified adaptive random search method is successfully employed to solve the problem. Cam lobe area could be increased up to 7.3% without any penalties in kinematic and dynamic behaviors of the valve train.

• 한국항행학회논문지
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• 제15권3호
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• pp.441-448
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• 2011

엔진 밸브 트레인 계는 다수의 밸브 부품 시스템으로 구성되어 있어서 동적 특성을 나타내는 방정식을 세우고 그 거동을 정확히 정의 및 제시하는 것이 매우 중요하다. 엔진 작동 상태에서 밸브 트레인 시스템이 이상적으로 작동하기 위해서는 밸브의 간극 유지, 부품의 내열성 및 내마모성 등도 많은 영향을 끼치지만 기본적으로 캠 형상이 밸브 트레인 계의 동적 거동 특성에 미치는 영향이 매우 크다. 기본적으로 캠 거동 곡선을 표현하기 위해서는 폴리노미얼 캠, 멀티폴 캠 또는 폴리다인 캠 곡선을 사용하는데, 본 연구에서는 고속으로 작동하는 엔진의 동적 특성을 가장 잘 표현하는 폴리다인 캠 프로파일 방정식을 이용하여 기하학적인 모델링과 수학적 해석을 전개하여 각 변수가 밸브 거동에 미치는 영향을 제시하였다.

• 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.

• 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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• 제12권6호
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• pp.1-8
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• 2004

In this paper we present the effects that valve train design parameters and operating conditions have on the valve rotation properties of a diesel engine. Rotation of intake and exhaust valves are very closely related to the long term durability of diesel engines. of 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. Because the rated speed of a diesel engine is relatively lower than that of a gasoline engine, the operating condition of a diesel engine produces tough environment for valve rotation. Therefore, the valve rotation is an important problem which should be solved in the early stage of engine development. In this study, we developed a new technique to measure the valve rotation and shaking motion simultaneously using three proximity sensors. Valve train rotating properties of a diesel engine were measured under various engine operating conditions.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.258-262
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• 2000

This paper reports on the development of the analysis program of the valve train system, IV-TAP. It is essential to verify the stability of the design and to improve the performance of the system. In order to do that effi챠ently, it is required that integrated and interactive simulation analysis program. IV-TAP is developed in the base of the object-oriented, capsulation, modulization, OLE(objected linking and embedding) and variational design theory. So it contain the expandability and flexibility of the structure. In additon to that, it is programed to make the convenient user interface by using the visualization programming. It can support the modification of the valve element as well as the development of the valve system in the beginning. It is expected to reduce the money and effort for design the valve train system.