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

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05d
• /
• pp.327-332
• /
• 1996

대구경유압식스너버의 잠재적 기능상실은 미국원자력규제위원회(USNRC)에서 인정한 주요안 전성 문제중의 하나이다. 본 보고서는 한국표준형원전의 증기발생기와 원자로냉각재펌프에 설치되어있는 대구경유압식스너버 중 단일 스너버의 기능상실에 대하여 지진과 가상분기관파단의 시간이력해석을 수행하여 구조적영향을 보였다. 지진 입력은 SRP 3.7.1 에 따른 가상적 시간이력이며, 분기관파단 입력은 파단전누설기법(Leak Before Break) 적용에 의하여 배제되지 못한 분기관파 단인 증기발생기 주증기배관과 증기발생기 주급수배관의 가상파단을 이용하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2007.04a
• /
• pp.59-60
• /
• 2007

전기 정유압장치는 밸브플레이트, 실린더 배럴, 피스톤, 샤프트등으로 이루어진 유압펌프의 부품에 요구되는 기계적 성질을 향상하기위하여 이온 질화를 포함한 다양한 연구가 진행 되어지고 있다. 그러나 본실험에서는 이온질화시 발생하는 열변형등의 단점을 해결하기 위하여 PVD 박막을 실시하여 유압펌프 부품의 마모특성 향상에 관한 연구를 실시하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.2
• /
• pp.49-56
• /
• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is a combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. In this paper the effect of transformer is studied. Multiple closed loop controllers with displacement feedback of variable pump/motor, speed feedback and position feedback of cylinder are used. The efficiency and energy consumption when cylinder is driven up and down is calculated by simulation. Simulation results show that considerable energy saving is achieved by choosing load ratio, circuit type and supply pressure.

• Aerospace Engineering and Technology
• /
• v.8 no.2
• /
• pp.54-60
• /
• 2009

Qualification test items and those certification procedures of aircraft hydraulic pump are investigated in this report. Weight minimization through optimal design of aircraft hydraulic pump and its certification process investigation are very important. In this report, some fundamental performance data was presumed for the normal aircraft hydraulic pump, and then basic procedures for qualification tests are presented.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.3
• /
• pp.33-38
• /
• 2002

This paper deals with pressure ripple attenuation far separated-type Hydrostatic Transmission (HST) consisting ova variable axial piston pump connected in an open loop to a fried displacement axial piston motor. Pressure ripples in HST is major source of vibration which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube tripe hydraulic filter is proposed to attenuate pressure ripples with the high frequencies components to achieve better noise reduction in HST. The basic principle of a hydraulic filter is allied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimentally shown that the hydraulic filter attenuates about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and provide a means of designing a quieter HST.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.405-410
• /
• 1999

Hydraulic pipeline between servo valve and actuator affect the dynamic characteristics of electrohydraulic servo systems in serveral ways. This paper deal with the speed control of oil hydraulic gear motor using electrohydraulic servo valve. The frequency and transient response of electrohydraulic servo valve coupled to a gear motor is anlayzed. In particular, the effect of short and long hydraulic pipelines between servo valve and gear motor is investigated. The dynamic characteristics of the speed control systems of gear motor with short pipeline is first described via frequency response experiments with small signal linearized analysis. Loner pipeline is applied distributed parameter pipeline model with consideration of frequency dependent viscous friction.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.917-922
• /
• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.757-762
• /
• 1994

본 연구에서는 정밀진단가공을 위한 파인 블랭킹 기술 개발을 위한 파인 블랭킹용 전용 프레스를 사용 하지 않고 범용 유압 프레스에서 조보 유압 장치에 의해 압력을 조절해가면서 가공특성에 관한 실험적 연구와 이론 해석을 수행한다. 실험을 위해 파인 블랭킹 금형과 유압 장치를 설계 제작하고, 정밀진단 특성에 제일 큰 영향을 미치고 있는 V-돌기( Vee-ring)의 유무와 위치 그리고 스트리핑력 및 카운터 펀 칭력 변화에 따른 제품 정밀도를 조사해 가면서 최적의 정밀도 예측 수단으로 적절함을 확인할 수 있었으며, 실험결과는 작업 조건에 관계없이 모든 제품이 깨끗한 전단면을 나타내고 있으며, 일반적으로 스트리핑력이 감소할수록, 그리고 카운터 펀칭력이 증가할수록 캠버량이 감소하고 특히 카운터 펀칭력에 큰 영향을 받고 있음을 알 수 있었다. 이와같은 현상은 유한 요소해석에 의한 캠버량의 예측에섣고 정성적으로 잘 일치하고 있는 것으로 나타났다.

• Journal of Drive and Control
• /
• v.11 no.4
• /
• pp.39-45
• /
• 2014

With recent oil price increases, the fuel efficiency of hydraulic excavators has become a serious issue. Researchers have considered weight lightening by high pressurization in order to improve the efficiency of the excavator and pump controlled actuation (PCA) and to reduce pressure loss of hybrid and valves using mechanical inertia. However, high pressurization is not very effective because the excavator operates at a low speed; a hybrid is inefficient because little accumulated inertial energy is accumulated; and PCA is ineffective because control precision and responsibility are low. In this study, a method to minimize air and gas in hydraulic oil has been presented as a simple and new way to increase hydraulic efficiency.