• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.218-223
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• 1997

유압장치의 핵심부품인 유압 제어밸브(hydraulic control valve)는 유압펌프 등에 의하여 가압된 유압유의 압력과 유량을 제어하고 유동방향을 변화시키는 주요기능을 수행한다. 특히, 대부분의 제어밸브는 스푸울(spool)과 슬리브(sleeve)를 기본구조로 채용하고 있다. 피스톤 형상인 스푸울이 슬리브내를 왕복운동하면 스푸울과 슬리브 사이의 간극(clearance)에서는 점성유체인 유압유의 윤활작용에 의하여 원주방향으로 비대칭인 유체압력이 발생한다. 이 결과로 스푸울에 측력(lateral force)이 작용하며, 조건에 따라서는 스푸울에 작용하며, 조건에 따라서는 스푸울에 작용하는 마찰력이 증대할 뿐만 아니라 스푸울과 슬리브의 내벽에 과도한 마멸(wear)을 유방시키기도 하여 제어밸브의 성능을 크게 저하시키기도 한다. 유압공학분야서는 이를 유체고착(hydraulic locking) 현상이라고 부른다. 본 논문에서는 항공기 Flap actuator의 Selector manifold에서 사용되는 스푸울 밸브의 성능에 큰 영향을 미칠 것으로 예상되는 스프울과 슬리브 사이 간극에서의 윤활특성을 이론적으로 조사하고자 한다.

• Journal of the KSME
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• v.17 no.1
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• pp.28-31
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• 1977

유압밸브의 스푸울(spool)에 작용하는 유동력을 정확하게 기술하는 것은 일반적으로 매우어렵고, 실험에 의존하는 경우가 많다. 수푸울의 형상이 비교적 간단한 경우에 대해서는, 적절한 가정하에 서 유동력의 크기를 계산할 수 있고, 그 결과를 설계에 이용할 수 있다. 많은 유압교과서에서 유 동력의 기술을 다루고 있으나 기술방법에 있어서 명확성이 결여된 느낌을 주는 경우가 많고, 가 끔 학생들이나 현장의 기술자들이 유동력의 개년메 대해서 혼돈하는 수가 있다. 이 글의 내용은 본인의 유압공학 강의에서 발춰, 정리한 것이고, 유압백브에 작용하는 유동력의 명확한 이해를 주 기 위해서 쓴 것이므로 앞으로 이 분야에 종사하는 사람들에게 참고가 되기를 희망한다. 여기서 다루는 문제는 유압밸브의 스푸울에 작용하는 반경방향의 유동력(Iateral forces)과 축방향의 힘 (axial forces), 포펫트형(popet type) 밸브에 미치는 유동력, 후렛퍼형(flapper) 밸브에 작용하는 힘 등이고 기하학적 형태가 간단한 경우에 대해서 논의한다.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.54-68
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• 2018

The objective of this study is to analyze the effect of dynamic characteristics of the check valve applied to the small piezoelectric-hydraulic pumps on flow rate formation. The flow rate of the piezoelectric-hydraulic pump is a key factor in the formation of the load pressure to operate the brake system. At this time, the natural frequency of the check valve operating in the fluid has a great influence on the formulation of the flow rate of the piezoelectric-hydraulic pump. In addition, the natural frequency of the check valve is affected by the gap between the check valve and the pump seat. In this study, the natural frequency of the check valve according to the gap between the check valve and the pump seat was calculated through the fluid-structure interaction analysis. The flow rate obtained from the simulation result was verified by comparing it with the result from the flow rate experiment using the developed piezoelectric-hydraulic pump.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.15-24
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• 1986

Pressure trasients must deal with safety problem of system. For identification of physical situation that can and method of limiting surges are essential consideration in sucessful design. The finite difference equation by method of characteristics are derived from the governing equation of unsteady flow in a pipe, and solved by using boundary condition derived. A computer program which can simulate general hydraulic system is developed by using finite difference equations and boundary conditions derived. The sumulated resulted by developed computer program are in fair agreement with experiment result.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.28-35
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• 2017

Recently, conventional hydraulic car lift systems face the technological limitations due to a lack of height control. The demand for height controllability is required in many tasks such as wheel alignment, and requires compensation for the structural deformation of the lift caused by irregular load distribution. In order to resolve this limitation of the conventional car lift, in this work, a new type of a hydraulic vehicle lift using a magneto-rheological (MR) valve system is proposed and analyzed. Firstly, the dynamic model of vehicle lift is formulated to evaluate control performance; subsequently, an MR valve is designed to obtain the desired pressure drop required in the car lift. Next, a proportional-integral-derivative (PID) controller is formulated to achieve accurate control of the lifting height and then computer simulations are undertaken to show accurate height control performances of the proposed new car lift system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3869-3875
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• 2012

In this study, mathematical modeling and experimental analysis were executed in order to evaluate the valve dynamic characteristics when the hydraulic pressure applied. High pressure on the master cylinder effects on the valve dynamic characteristics have been analyzed. The pulsation pressure generated in hydraulic systems causes noise, vibration and odd effect to the system. To reduce the pulsation pressure, high frequency PWM control of 20KHz was attempted. Also, an analytic method is proposed for the resultant forces of electromagnetism and hydraulic pressure generated in the real vehicle electro stability program. Consequently, results of solenoid valve dynamic characteristics analysis derived in the study can be confirmed criteria for the optimal control of electronic stability program system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.475-482
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• 2014

The precision hydraulic valve is widely used in various industrial field like aircraft, automobile, and general machinery. Servo actuator is the most important device for driving the precise hydraulic valve. The reliable operation of servo actuator effects on the overall hydraulic system. The performance of servo actuator relies on frequency response and step response according to arbitrary input signal. In this paper, we performed the analysis for the components of servo actuator to satisfy the reliable operation and response characteristics through the reliability analysis, and also induced the design parameters to realize the reliable operation and fast response characteristics of servo actuator for hydraulic valve operation through the empirical knowledge of experts and electromagnetic theories. We suggested the design equations to determine the values of design parameters of servo actuator as like bobbin size, length of yoke and plunger and turn number of coil, and verified the achieved design values through FEM analysis and performance tests using some prototypes of servo actuators adapted in hydraulic valve.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.30-38
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• 1991

자동차의 제동장치, 조향장치, 자동 변속장치 등에 요구되는 큰 힘을 얻기 위하여 유압식 구동장치가 중량당 출력비가 높고 응답특성이 좋으며 과부하에 대한 방지기능이 간단하게 이루어 진다는 장점이 있기 때문이다. 본 고에서는 우리나라에서도 전자제어식 제동장치, 조향장치, 자동변속장치, 현가장치 등의 개발을 시도하고 있는 현 시점에서 기술축적이 가장 취약한 분야라고 볼 수 있는 자동차용 전기유압밸브의 기본적인 메카니즘에 대하여 종합적으로 소개하고자 한다.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.760-766
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• 2010

In this paper, The static friction torque and viscous friction torque including hydraulic motor-load system driven by hydraulic proportional control valve analysis. The basic experimental was performed toward characteristic in pressure and flow rate in hydraulic system energy. The variable of friction torque was experiment on brake pressure variable using pneumatic brake system. The analysis of nonlinear friction and linear friction was perform ed toward friction characteristic of hydraulic system.

• Journal of Drive and Control
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• v.18 no.4
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• pp.92-97
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• 2021